#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}


struct FastIO{
  FastIO(){
    cin.tie(0);
    ios::sync_with_stdio(0);
  }
}fastio_beet;


template<typename T,T MOD = 1000000007>
struct Mint{
  static constexpr T mod = MOD;
  T v;
  Mint():v(0){}
  Mint(signed v):v(v){}
  Mint(long long t){v=t%MOD;if(v<0) v+=MOD;}

  Mint pow(long long k){
    Mint res(1),tmp(v);
    while(k){
      if(k&1) res*=tmp;
      tmp*=tmp;
      k>>=1;
    }
    return res;
  }

  static Mint add_identity(){return Mint(0);}
  static Mint mul_identity(){return Mint(1);}

  Mint inv(){return pow(MOD-2);}

  Mint& operator+=(Mint a){v+=a.v;if(v>=MOD)v-=MOD;return *this;}
  Mint& operator-=(Mint a){v+=MOD-a.v;if(v>=MOD)v-=MOD;return *this;}
  Mint& operator*=(Mint a){v=1LL*v*a.v%MOD;return *this;}
  Mint& operator/=(Mint a){return (*this)*=a.inv();}

  Mint operator+(Mint a) const{return Mint(v)+=a;};
  Mint operator-(Mint a) const{return Mint(v)-=a;};
  Mint operator*(Mint a) const{return Mint(v)*=a;};
  Mint operator/(Mint a) const{return Mint(v)/=a;};

  Mint operator-() const{return v?Mint(MOD-v):Mint(v);}

  bool operator==(const Mint a)const{return v==a.v;}
  bool operator!=(const Mint a)const{return v!=a.v;}
  bool operator <(const Mint a)const{return v <a.v;}

  static Mint comb(long long n,int k){
    Mint num(1),dom(1);
    for(int i=0;i<k;i++){
      num*=Mint(n-i);
      dom*=Mint(i+1);
    }
    return num/dom;
  }
};
template<typename T,T MOD> constexpr T Mint<T, MOD>::mod;
template<typename T,T MOD>
ostream& operator<<(ostream &os,Mint<T, MOD> m){os<<m.v;return os;}


template<typename V>
V compress(V v){
  sort(v.begin(),v.end());
  v.erase(unique(v.begin(),v.end()),v.end());
  return v;
}
template<typename T>
map<T, int> dict(const vector<T> &v){
  map<T, int> res;
  for(int i=0;i<(int)v.size();i++)
    res[v[i]]=i;
  return res;
}
map<char, int> dict(const string &v){
  return dict(vector<char>(v.begin(),v.end()));
}

template<typename T>
struct FormalPowerSeries{
  using Poly = vector<T>;
  using Conv = function<Poly(Poly, Poly)>;
  Conv conv;
  FormalPowerSeries(Conv conv):conv(conv){}

  Poly pre(const Poly &as,int deg){
    return Poly(as.begin(),as.begin()+min((int)as.size(),deg));
  }

  Poly add(Poly as,Poly bs){
    int sz=max(as.size(),bs.size());
    Poly cs(sz,T(0));
    for(int i=0;i<(int)as.size();i++) cs[i]+=as[i];
    for(int i=0;i<(int)bs.size();i++) cs[i]+=bs[i];
    return cs;
  }

  Poly sub(Poly as,Poly bs){
    int sz=max(as.size(),bs.size());
    Poly cs(sz,T(0));
    for(int i=0;i<(int)as.size();i++) cs[i]+=as[i];
    for(int i=0;i<(int)bs.size();i++) cs[i]-=bs[i];
    return cs;
  }

  Poly mul(Poly as,Poly bs){
    return conv(as,bs);
  }

  Poly mul(Poly as,T k){
    for(auto &a:as) a*=k;
    return as;
  }

  // F(0) must not be 0
  Poly inv(Poly as,int deg){
    assert(as[0]!=T(0));
    Poly rs({T(1)/as[0]});
    for(int i=1;i<deg;i<<=1)
      rs=pre(sub(add(rs,rs),mul(mul(rs,rs),pre(as,i<<1))),i<<1);
    return rs;
  }

  // not zero
  Poly div(Poly as,Poly bs){
    while(as.back()==T(0)) as.pop_back();
    while(bs.back()==T(0)) bs.pop_back();
    if(bs.size()>as.size()) return Poly();
    reverse(as.begin(),as.end());
    reverse(bs.begin(),bs.end());
    int need=as.size()-bs.size()+1;
    Poly ds=pre(mul(as,inv(bs,need)),need);
    reverse(ds.begin(),ds.end());
    return ds;
  }

  // F(0) must be 1
  Poly sqrt(Poly as,int deg){
    assert(as[0]==T(1));
    T inv2=T(1)/T(2);
    Poly ss({T(1)});
    for(int i=1;i<deg;i<<=1){
      ss=pre(add(ss,mul(pre(as,i<<1),inv(ss,i<<1))),i<<1);
      for(T &x:ss) x*=inv2;
    }
    return ss;
  }

  Poly diff(Poly as){
    int n=as.size();
    Poly rs(n-1);
    for(int i=1;i<n;i++) rs[i-1]=as[i]*T(i);
    return rs;
  }

  Poly integral(Poly as){
    int n=as.size();
    Poly rs(n+1);
    rs[0]=T(0);
    for(int i=0;i<n;i++) rs[i+1]=as[i]/T(i+1);
    return rs;
  }

  // F(0) must be 1
  Poly log(Poly as,int deg){
    return pre(integral(mul(diff(as),inv(as,deg))),deg);
  }

  // F(0) must be 0
  Poly exp(Poly as,int deg){
    Poly f({T(1)});
    as[0]+=T(1);
    for(int i=1;i<deg;i<<=1)
      f=pre(mul(f,sub(pre(as,i<<1),log(f,i<<1))),i<<1);
    return f;
  }

  Poly partition(int n){
    Poly rs(n+1);
    rs[0]=T(1);
    for(int k=1;k<=n;k++){
      if(1LL*k*(3*k+1)/2<=n) rs[k*(3*k+1)/2]+=T(k%2?-1LL:1LL);
      if(1LL*k*(3*k-1)/2<=n) rs[k*(3*k-1)/2]+=T(k%2?-1LL:1LL);
    }
    return inv(rs,n+1);
  }

  Poly bernoulli(int n){
    Poly rs(n+1,1);
    for(int i=1;i<=n;i++) rs[i]=rs[i-1]/T(i+1);
    rs=inv(rs,n+1);
    T tmp(1);
    for(int i=1;i<=n;i++){
      tmp*=T(i);
      rs[i]*=tmp;
    }
    return rs;
  }
};

template<typename M>
class Enumeration{
private:
  static vector<M> fact,finv,invs;
public:
  static void init(int n){
    n=min<decltype(M::mod)>(n,M::mod-1);

    int m=fact.size();
    if(n<m) return;

    fact.resize(n+1,1);
    finv.resize(n+1,1);
    invs.resize(n+1,1);

    if(m==0) m=1;
    for(int i=m;i<=n;i++) fact[i]=fact[i-1]*M(i);
    finv[n]=M(1)/fact[n];
    for(int i=n;i>=m;i--) finv[i-1]=finv[i]*M(i);
    for(int i=m;i<=n;i++) invs[i]=finv[i]*fact[i-1];
  }

  static M Fact(int n){
    init(n);
    return fact[n];
  }
  static M Finv(int n){
    init(n);
    return finv[n];
  }
  static M Invs(int n){
    init(n);
    return invs[n];
  }

  static M C(int n,int k){
    if(n<k||k<0) return M(0);
    init(n);
    return fact[n]*finv[n-k]*finv[k];
  }

  static M P(int n,int k){
    if(n<k||k<0) return M(0);
    init(n);
    return fact[n]*finv[n-k];
  }

  static M H(int n,int k){
    if(n<0||k<0) return M(0);
    if(!n&&!k) return M(1);
    init(n+k-1);
    return C(n+k-1,k);
  }

  static M S(int n,int k){
    init(k);
    M res(0);
    for(int i=1;i<=k;i++){
      M tmp=C(k,i)*M(i).pow(n);
      if((k-i)&1) res-=tmp;
      else res+=tmp;
    }
    return res*=finv[k];
  }

  static vector< vector<M> > D(int n,int m){
    vector< vector<M> > dp(n+1,vector<M>(m+1,0));
    dp[0][0]=M(1);
    for(int i=0;i<=n;i++){
      for(int j=1;j<=m;j++){
        if(i-j>=0) dp[i][j]=dp[i][j-1]+dp[i-j][j];
        else dp[i][j]=dp[i][j-1];
      }
    }
    return dp;
  }

  static M B(int n,int k){
    if(n==0) return M(1);
    k=min(k,n);
    init(k);
    vector<M> dp(k+1);
    dp[0]=M(1);
    for(int i=1;i<=k;i++)
      dp[i]=dp[i-1]+((i&1)?-finv[i]:finv[i]);
    M res(0);
    for(int i=1;i<=k;i++)
      res+=M(i).pow(n)*finv[i]*dp[k-i];
    return res;
  }

  static M montmort(int n){
    init(n);
    M res(0);
    for(int k=2;k<=n;k++){
      if(k&1) res-=finv[k];
      else res+=finv[k];
    }
    return res*=fact[n];
  }

  static M LagrangePolynomial(vector<M> &y,M t){
    int n=y.size()-1;
    if(t.v<=n) return y[t.v];
    init(n+1);
    vector<M> dp(n+1,1),pd(n+1,1);
    for(int i=0;i<n;i++) dp[i+1]=dp[i]*(t-M(i));
    for(int i=n;i>0;i--) pd[i-1]=pd[i]*(t-M(i));
    M res(0);
    for(int i=0;i<=n;i++){
      M tmp=y[i]*dp[i]*pd[i]*finv[i]*finv[n-i];
      if((n-i)&1) res-=tmp;
      else res+=tmp;
    }
    return res;
  }
};
template<typename M>
vector<M> Enumeration<M>::fact=vector<M>();
template<typename M>
vector<M> Enumeration<M>::finv=vector<M>();
template<typename M>
vector<M> Enumeration<M>::invs=vector<M>();


constexpr int bmds(int x){
  const int v[] = {1012924417, 924844033, 998244353,
                   897581057, 645922817};
  return v[x];
}
constexpr int brts(int x){
  const int v[] = {5, 5, 3, 3, 3};
  return v[x];
}

template<int X>
struct NTT{
  static constexpr int md = bmds(X);
  static constexpr int rt = brts(X);
  using M = Mint<int, md>;
  vector< vector<M> > rts,rrts;

  void ensure_base(int n){
    if((int)rts.size()>=n) return;
    rts.resize(n);rrts.resize(n);
    for(int i=1;i<n;i<<=1){
      if(!rts[i].empty()) continue;
      M w=M(rt).pow((md-1)/(i<<1));
      M rw=w.inv();
      rts[i].resize(i);rrts[i].resize(i);
      rts[i][0]=M(1);rrts[i][0]=M(1);
      for(int k=1;k<i;k++){
        rts[i][k]=rts[i][k-1]*w;
        rrts[i][k]=rrts[i][k-1]*rw;
      }
    }
  }

  void ntt(vector<M> &as,bool f,int n=-1){
    if(n==-1) n=as.size();
    assert((n&(n-1))==0);
    ensure_base(n);

    for(int i=0,j=1;j+1<n;j++){
      for(int k=n>>1;k>(i^=k);k>>=1);
      if(i>j) swap(as[i],as[j]);
    }

    for(int i=1;i<n;i<<=1){
      for(int j=0;j<n;j+=i*2){
        for(int k=0;k<i;k++){
          M z=as[i+j+k]*(f?rrts[i][k]:rts[i][k]);
          as[i+j+k]=as[j+k]-z;
          as[j+k]+=z;
        }
      }
    }

    if(f){
      M tmp=M(n).inv();
      for(int i=0;i<n;i++) as[i]*=tmp;
    }
  }

  vector<M> multiply(vector<M> as,vector<M> bs){
    int need=as.size()+bs.size()-1;
    int sz=1;
    while(sz<need) sz<<=1;
    as.resize(sz,M(0));
    bs.resize(sz,M(0));

    ntt(as,0);ntt(bs,0);
    for(int i=0;i<sz;i++) as[i]*=bs[i];
    ntt(as,1);

    as.resize(need);
    return as;
  }

  vector<int> multiply(vector<int> as,vector<int> bs){
    vector<M> am(as.size()),bm(bs.size());
    for(int i=0;i<(int)am.size();i++) am[i]=M(as[i]);
    for(int i=0;i<(int)bm.size();i++) bm[i]=M(bs[i]);
    vector<M> cm=multiply(am,bm);
    vector<int> cs(cm.size());
    for(int i=0;i<(int)cs.size();i++) cs[i]=cm[i].v;
    return cs;
  }
};
template<int X> constexpr int NTT<X>::md;
template<int X> constexpr int NTT<X>::rt;


struct ArbitraryModConvolution{
  using ll = long long;
  static NTT<0> ntt0;
  static NTT<1> ntt1;
  static NTT<2> ntt2;

  static constexpr int pow(int a,int b,int md){
    int res=1;
    a=a%md;
    while(b){
      if(b&1) res=(ll)res*a%md;
      a=(ll)a*a%md;
      b>>=1;
    }
    return res;
  }

  static constexpr int inv(int x,int md){
    return pow(x,md-2,md);
  }

  inline void garner(int &c0,int c1,int c2,int m01,int MOD){
    static constexpr int r01=inv(ntt0.md,ntt1.md);
    static constexpr int r02=inv(ntt0.md,ntt2.md);
    static constexpr int r12=inv(ntt1.md,ntt2.md);

    c1=(ll)(c1-c0)*r01%ntt1.md;
    if(c1<0) c1+=ntt1.md;

    c2=(ll)(c2-c0)*r02%ntt2.md;
    c2=(ll)(c2-c1)*r12%ntt2.md;
    if(c2<0) c2+=ntt2.md;

    c0+=(ll)c1*ntt0.md%MOD;
    if(c0>=MOD) c0-=MOD;
    c0+=(ll)c2*m01%MOD;
    if(c0>=MOD) c0-=MOD;
  }

  inline void garner(vector< vector<int> > &cs,int MOD){
    int m01 =(ll)ntt0.md*ntt1.md%MOD;
    int sz=cs[0].size();
    for(int i=0;i<sz;i++) garner(cs[0][i],cs[1][i],cs[2][i],m01,MOD);
  }

  vector<int> multiply(vector<int> as,vector<int> bs,int MOD){
    vector< vector<int> > cs(3);
    cs[0]=ntt0.multiply(as,bs);
    cs[1]=ntt1.multiply(as,bs);
    cs[2]=ntt2.multiply(as,bs);
    size_t sz=as.size()+bs.size()-1;
    for(auto& v:cs) v.resize(sz);
    garner(cs,MOD);
    return cs[0];
  }

  template<typename T,T MOD>
  decltype(auto) multiply(vector< Mint<T, MOD> > am,
                          vector< Mint<T, MOD> > bm){
    using M = Mint<T, MOD>;
    vector<int> as(am.size()),bs(bm.size());
    for(int i=0;i<(int)as.size();i++) as[i]=am[i].v;
    for(int i=0;i<(int)bs.size();i++) bs[i]=bm[i].v;
    vector<int> cs=multiply(as,bs,MOD);
    vector<M> cm(cs.size());
    for(int i=0;i<(int)cm.size();i++) cm[i]=M(cs[i]);
    return cm;
  }
};
NTT<0> ArbitraryModConvolution::ntt0;
NTT<1> ArbitraryModConvolution::ntt1;
NTT<2> ArbitraryModConvolution::ntt2;

//INSERT ABOVE HERE
const int MOD = 1e9+7;
using M = Mint<int, MOD>;

M dp[256][512]={};
M nx[256][512]={};

signed main(){
  int n;
  cin>>n;
  vector<int> as(n),bs(n);
  for(int i=0;i<n;i++) cin>>as[i]>>bs[i];

  vector<int> vs;
  for(int a:as) vs.emplace_back(a);
  for(int b:bs) vs.emplace_back(b);
  vs.emplace_back(0);
  vs.emplace_back(1e9+6);

  vs=compress(vs);
  auto dc=dict(vs);
  int sz=dc.size();

  ArbitraryModConvolution arb;
  FormalPowerSeries<M> FPS([&](auto as,auto bs){return arb.multiply(as,bs);});

  using Poly = FormalPowerSeries<M>::Poly;

  vector<int> ukunichia({1,1,1,2,5,16,61,271,1372,7795,49093,339386,2554596,20794982,182010945,704439023,3262351,11278075,683250715,55183828,723559623,493873264,82870793,349118277,457295903,720607889,110619008,451099916,530345692,290476770,764082888,26991108,704329333,561191326,86908956,111729500,82430516,585014834,580637148,21817387,242423923,603656795,188683177,516392604,217523158,627591779,20167390,776981024,253806183,855526133,981202686,733581864,394424968,581604317,664818054,733303056,884774302,877161056,905111853,734209913,212095039,312905303,531382421,931612958,184986793,367052446,474127658,593690875,584355790,181431808,218111480,54000002,451980771,381000342,594719901,220408770,239302554,153215746,767122471,366413638,230747940,928708626,120479836,810346140,239696337,423652316,365007320,744876087,881577589,253229888,401479167,11601389,857110894,95223477,765392401,309903247,697686481,246345553,54984377,850384943,753833055,979686540,542115189,17444401,606213958,614700905,428276325,420269353,961409430,723909764,370083014,668516350,80667438,2145321,759296465,411967068,491591351,954814537,859056672,370660223,412709206,270471839,393386854,554502386,703744007,730501201,492831815,338687790,846144592,796787144,471915137,104783411,800034213,449133848,934294003,281056826,219512969,243710164,702898601,62636663,214488750,238633697,685069898,683432242,537877794,872915701,134638129,666271225,482324163,354370925,33527887,274837718,471993274,131490707,449021612,880570764,96750566,95630301,709622796,684037338,181785418,543181519,707207288,147845108,734734418,474355557,835779334,15846979,925902318,400223968,258585356,398493156,962176674,584791048,992521860,430094639,464075516,176594798,304135055,865521046,255948297,570870408,86905809,219536521,801833040,784222115,136425629,988462293,207388365,871730918,975161979,556587288,482255125,414891003,280579686,519728728,248706613,793936755,800711772,233227046,395574000,598333036,86618062,634795701,475575027,704117114,325285408,759201663,336817467,697491978,253031400,949838275,960326369,433878278,567786607,828970321,911326548,902915359,942098237,166504068,167153382,421681089,284731510,503467289,801365240,327454625,302747534,327035677,360000988,970256866,285746586,362634059,852252072,195930619,899837522,512085131,198984584,892863449,354264608,148815500,409868290,944832231,890388825,56375456,818865220,462277760,20363120,550072594,173243785,830067831,28037738,961538660,33607870,182684796,33390178,74658547,864175106,529134490,392280763,945544595,950979164,884342407,647050591,529910163,300483207,899891775,230574188,946707843,836911201,115959771,378899311,700787303,315758098,75292821,859998219,509229496,14668408,622151258,70877884,750844692,883209674,368806072,645552403,520596813,566008687,79728920,717123558,246655702,708305179,514197351,192660503,445281817,467790070,948018227,501854603,610330053,23346235,554926802,552086835,614256402,122881879});
  Poly sum;
  M acc{1};
  int cnt=0;
  for(int v:ukunichia){
    sum.emplace_back(v);
    sum.back()/=acc;
    cnt++;
    acc*=M(cnt);
  }

  //cout<<sum.size()<<endl;
  /*//
  const int deg = 1<<7;
  if(n>=deg) exit(0);
  {
    sum=Poly({});
    for(int l=0;l<deg;l++){
      Poly res({M(1)});
      Poly bs({M(1),M(1)});
      bs=FPS.inv(bs,deg);
      Poly tmp({M(1)});
      for(int i=1;i<=l;i++){
        tmp=FPS.pre(FPS.mul(tmp,bs),deg);
        res=FPS.pre(FPS.mul(res,FPS.sub(Poly({M(1)}),tmp)),deg);
      }
      sum=FPS.add(sum,res);
    }
    using E = Enumeration<M>;
    E::init(deg);
    //for(int i=0;i<deg;i++) cout<<sum[i]<<endl;
    for(int i=0;i<deg;i++) sum[i]*=E::Finv(i);
    //for(int i=0;i<deg;i++) cout<<sum[i]<<",";
  }
  //*/

  for(int j=0;j+1<sz;j++)
    if(as[0]<=vs[j]&&vs[j+1]<=bs[0])
      dp[1][j]=M(vs[j+1]-vs[j])/M(bs[0]-as[0]);

  for(int i=1;i<n;i++){
    M rev=M(bs[i]-as[i]).inv();

    vector<M> cof(sz,0);
    for(int j=0;j+1<sz;j++)
      cof[j]=M(as[i]<=vs[j]&&vs[j+1]<=bs[i])*M(vs[j+1]-vs[j])*rev;

    if(i&1){
      for(int l=1;l<n;l++){
        M tmp{0};
        for(int j=0;j+1<sz;j++){
          nx[l+1][j]+=dp[l][j]*cof[j];

          nx[1][j]+=tmp;
          tmp+=sum[l]*dp[l][j];
        }
      }
      for(int k=0;k+1<sz;k++) nx[1][k]*=cof[k];
    }else{
      for(int l=1;l<n;l++){
        M tmp{0};
        for(int j=sz-2;j>=0;j--){
          nx[l+1][j]+=dp[l][j]*cof[j];

          nx[1][j]+=tmp;
          tmp+=sum[l]*dp[l][j];
        }
      }
      for(int k=0;k+1<sz;k++) nx[1][k]*=cof[k];
    }

    for(int j=0;j<256;j++)
      for(int k=0;k<512;k++)
        dp[j][k]=nx[j][k],nx[j][k]=M(0);
  }

  M ans{0};
  for(int i=1;i<=n;i++)
    for(int j=0;j+1<sz;j++)
      ans+=dp[i][j]*sum[i];

  cout<<ans<<endl;
  return 0;
}