#include <iostream>
#include <cmath>
using namespace std;
typedef pair<int,int> Paint;
int main(){
  int n;cin>>n;
  Paint a[n];
  int sa = 0;
  int sma = 0;
  int smb = 0;
  for(int i = 0; n-1 > i; i++){
    int te,mp;cin>>te>>mp;
    sa += te-mp;
    sma += te;
    smb+=mp;
    a[i] = {te,mp};
  }
  cout << min(sma,smb)+1 << endl;
  

}