#include <cstdio>
#include <climits>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstdio>
#include <climits>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <utility>
#include <queue>
#include <cstring>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
const long long MOD = 1000000007;

typedef long long ll;

int
main(int argc, char *argv[])
{
  int n; cin >> n;
  int a = 0, b = 0;
  rep(i, n - 1) {
    int p, q;
    cin >> p >> q;
    a += p; b += q;
    
  }
  if (a > b) cout << a + 1 << endl;
    else cout << 2 * a - b + 1 << endl;
  return 0;
}