#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
const long long INF = std::numeric_limits<long long>::max();
const int MX = 100001;
const long double PI =
    3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270L;
template <typename T>
pair<T, T> operator+(const pair<T, T> &a, const pair<T, T> &b) {
  return pair<T, T>(a.first + b.first, a.second + b.second);
}
template <typename T>
pair<T, T> operator-(const pair<T, T> &a, const pair<T, T> &b) {
  return pair<T, T>(a.first - b.first, a.second - b.second);
}
template <typename T>
T operator*(const pair<T, T> &a, const pair<T, T> &b) {
  return (a.first * b.first + a.second * b.second);
}
template <typename T>
T operator^(const pair<T, T> &a, const pair<T, T> &b) {
  return (a.first * b.second - a.second * b.first);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int N;
  cin >> N;
  int a, b;
  int c = 0, d = 0;
  long long ats = 0;
  int last = -1;
  for (int i = 0; i < N; ++i) {
    cin >> a >> b;
    int maz = min(a, b);
    int did = max(c, d);
    if ((maz - did + 1) > 0) {
      ats += maz - did + 1 - int(last == did);
    }
    last = maz;
    c = a;
    d = b;
  }
  printf("%lld\n", ats);
}
