#include <bits/stdc++.h>   using namespace std;   const int N = 2e5 + 100, PI = 3.14159265359, M = 1e9 + 7;   long long a[N], ans = 1;   int main() {     long long n;     cin >> n;     long long x = 0, y = 0;     for (int i = 0; i < n; i++) {       long long a, b;       cin >> a >> b;       long long t1 = a - x, t2 = b - x;       if (x == y) {         ans += min(a, b) - x;       } else if (x < y) {         if (y <= a) {           x = y;           ans += min(a, b) - x + 1;         }       } else if (x > y) {         if (x <= b) {           y = x;           ans += min(a, b) - x + 1;         }       }       x = a, y = b;     }     cout << ans;   }   