#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1LL << (n))
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> bool mmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool mmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; }
template<typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
///// This part below is only for debug, not used /////
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;
///// END /////

template <int mod>
struct ModInt
{
    using lint = long long;
    int val;
    constexpr ModInt() : val(0) {}
    constexpr void _setval(lint v) { v = (v % mod) + mod; val = v >= mod ? v - mod : v; }
    constexpr ModInt(lint v) { _setval(v); }
    constexpr ModInt operator+(const ModInt &x) const { return ModInt((lint)val + x.val); }
    constexpr ModInt operator-(const ModInt &x) const { return ModInt((lint)val - x.val); }
    constexpr ModInt operator*(const ModInt &x) const { return ModInt((lint)val * x.val); }
    constexpr ModInt operator/(const ModInt &x) const { return ModInt((lint)val * x.inv()); }
    constexpr ModInt operator-() const { return ModInt(-val); }
    constexpr ModInt &operator+=(const ModInt &x) { return *this = *this + x; }
    constexpr ModInt &operator-=(const ModInt &x) { return *this = *this - x; }
    constexpr ModInt &operator*=(const ModInt &x) { return *this = *this * x; }
    constexpr ModInt &operator/=(const ModInt &x) { return *this = *this / x; }
    friend constexpr ModInt operator+(lint a, const ModInt &x) { return ModInt(a % mod + x.val); }
    friend constexpr ModInt operator-(lint a, const ModInt &x) { return ModInt(a % mod - x.val); }
    friend constexpr ModInt operator*(lint a, const ModInt &x) { return ModInt(a % mod * x.val); }
    friend constexpr ModInt operator/(lint a, const ModInt &x) { return ModInt(a % mod * x.inv()); }
    constexpr bool operator==(const ModInt &x) { return val == x.val; }
    constexpr bool operator!=(const ModInt &x) { return val != x.val; }
    friend istream &operator>>(istream &is, ModInt &x) { lint t; is >> t; x = ModInt(t); return is; }
    friend ostream &operator<<(ostream &os, const ModInt &x) { os << x.val;  return os; }

    constexpr lint power(lint n) const {
        lint ans = 1, tmp = this->val;
        while (n) {
            if (n & 1) ans = ans * tmp % mod;
            tmp = tmp * tmp % mod;
            n /= 2;
        }
        return ans;
    }
    constexpr lint inv() const { return this->power(mod - 2); }
    constexpr ModInt operator^(lint n) const { return ModInt(this->power(n)); }
    constexpr ModInt &operator^=(lint n) { return *this = *this ^ n; }

    inline ModInt fac() const {
        static vector<ModInt> facs;
        int l0 = facs.size();
        if (l0 > this->val) return facs[this->val];

        facs.resize(this->val + 1);
        for (int i = l0; i <= this->val; i++) facs[i] = (i == 0 ? ModInt(1) : facs[i - 1] * ModInt(i));
        return facs[this->val];
    }

    ModInt doublefac() const {
        lint k = (this->val + 1) / 2;
        if (this->val & 1) return ModInt(k * 2).fac() / ModInt(2).power(k) / ModInt(k).fac();
        else return ModInt(k).fac() * ModInt(2).power(k);
    }

    ModInt nCr(const ModInt &r) const {
        if (this->val < r.val) return ModInt(0);
        return this->fac() / ((*this - r).fac() * r.fac());
    }
};
using mint = ModInt<1000000007>;

vector<mint> calc_suc(int n)
{
    vector<mint> ret(n + 1);
    ret[0] = ret[1] = 1;
    FOR(i, 2, n + 1)
    {
        for (int j = 0; j < i; j += 2)
        {
            ret[i] += mint(1) / i * ret[j] * ret[i - 1 - j];
        }
    }
    return ret;
}

int main()
{
    int N;
    cin >> N;
    vector<int> A(N), B(N);
    vector<int> x;
    REP(i, N)
    {
        cin >> A[i] >> B[i];
        x.push_back(A[i]);
        x.push_back(B[i]);
    }
    sort(ALL(x));
    x.erase(unique(ALL(x)), x.end());
    int M = x.size();
    vector<vector<mint>> dp(M - 1, vector<mint>(N + 1));

    REP(i, M - 1) if (x[i] >= A[0] and x[i + 1] <= B[0])
    {
        dp[i][1] = mint(x[i + 1] - x[i]) / (B[0] - A[0]);
    }
    vector<mint> vsuc = calc_suc(201);
    FOR(i, 1, N)
    {
        vector<vector<mint>> dp_nxt(M - 1, vector<mint>(N + 1));
        REP(k, M - 1) if (A[i] <= x[k] and x[k + 1] <= B[i])
        {
            mint p = mint(x[k + 1] - x[k]) / (B[i] - A[i]);
            REP(j, M - 1)
            {
                if (j == k)
                {
                    FOR(suc, 1, i + 1) dp_nxt[k][suc + 1] = dp[j][suc] * p * vsuc[suc + 1] / vsuc[suc];
                }
                else
                {
                    if (i % 2 and j > k) continue;
                    if (i % 2 == 0 and j < k) continue;
                    FOR(suc, 1, i + 1) dp_nxt[k][1] += dp[j][suc] * p;
                }
            }
        }
        dp = dp_nxt;
    }
    mint ret = 0;
    for (auto vec : dp) ret += accumulate(ALL(vec), mint(0));
    cout << ret << endl;
}