/* -*- coding: utf-8 -*-
 *
 * 904.cc:  No.904 サメトロ - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  int asum = 0, bsum = 0;
  for (int i = 1; i < n; i++) {
    int ai, bi;
    scanf("%d%d", &ai, &bi);
    asum += ai, bsum += bi;
  }
  //printf("asum=%d, bsum=%d\n", asum, bsum);

  int da = bsum - max(0, bsum - asum);
  int db = asum - max(0, asum - bsum);
  printf("%d\n", min(da, db) + 1);
  return 0;
}