#include <bits/stdc++.h>
using namespace std;

using ll = long long;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  
  int n;
  cin >> n;
  
  ll ans = 0;
  for (int i = 0; i < n; i++) {
    ll a, b;
    cin >> a >> b;
    ans += abs(a - b);
  }
  
  cout << ans << '\n';
}