#include <bits/stdc++.h>
using namespace std;
const int M = 1e9 + 7;
const int MN = 1e6 + 6;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(10);
  long long n;
  cin >> n;
  long long p_x = 0, p_y = 0;
  long long res = 1;
  for (long long i = 0; i < n; ++i) {
    long long n_x, n_y;
    cin >> n_x >> n_y;
    if (p_x == n_x && p_y == n_y) continue;
    long long a = max(p_x, p_y);
    long long b = min(n_x, n_y);
    if (p_x == p_y) {
      a++;
    }
    if (a <= b) res += b - a + 1;
    p_x = n_x;
    p_y = n_y;
  }
  cout << res << endl;
  return 0;
}
