#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[8]={0,-1,0,1};
const ll dx[4]={-1,0,1,0};
template <typename T> inline bool chmax(T &a, T b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> inline bool chmin(T &a, T b) {
  return ((a > b) ? (a = b, true) : (false));
}
using ull=unsigned long long;
int main(){
  ll n;cin >> n;
  ll m=1563;
  ull dp[m];rep(i,m)dp[i]=0;dp[0]=1;
  rep(_,n){
    ll l,r;cin >> l >> r;
    bool flag=false;
    rep(i,m){
      if(flag)break;
      if(((i+1)<<6)-1<r)continue;
      if(__builtin_popcountl(dp[i])==0)continue;
      rep(j,64){
        if(dp[i]>>j&1){
          if(((i<<6)|j)>=r){
            dp[i]^=1ULL<<j;flag=true;break;
          }
        }
      }
    }
    per(i,m){
      if(l<=(i<<6)&&((i+1)<<6)<=r){
        if(dp[i]>>63&1)dp[i+1]|=1;
        dp[i]<<=1;
      }
      else if(((i+1)<<6)<=l||r<=(i<<6))continue;
      else{
        ll ns=0;
        rep(j,64){
          if(dp[i]>>j&1){
            if(l<=((i<<6)|j)&&((i<<6)|j)<r){
              if(j+1<64)ns|=1ULL<<(j+1);
            }
            else ns|=1ULL<<j;
          }
        }
        if(dp[i]>>63&1)if(((i<<6)|63)<r)dp[i+1]|=1;
        dp[i]=ns;
      }
    }
    dp[l>>6]|=1ULL<<(l&63);
    /*rep(i,64){
      if(dp[0]>>i&1)cout << i <<" ";
    }
    rep(i,64){
      if(dp[1]>>i&1)cout << i+64 <<" ";
    }
    cout << endl;*/
    //cout << bitset<64>(dp[1])  << bitset<64>(dp[0]) << endl;
  }
  ll ans=0;
  rep(i,m)ans+=__builtin_popcountl(dp[i]);
  cout << ans-1 << endl;
}