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

int main() {
  int n;
  cin>>n;
  int a_sum = 0, b_sum = 0;
  for (int i=0; i<n-1; i++) {
    int a, b;
    cin>>a>>b;
    a_sum += a;
    b_sum += b;
  }
  cout<<max(a_sum, b_sum) - abs(a_sum - b_sum) + 1<<endl;
}