#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;
  ll a[50], b[50];
  ll in = 0, out = 0;
  rep(i, n - 1) {
    cin >> a[i + 1] >> b[i + 1];
    in += a[i + 1]; out += b[i + 1];
  }
  if (in < out) {
    ll tmp;
    tmp = in; in = out; out = tmp;
    rep(i, n) {
      tmp = a[i];
      a[i] = b[i]; b[i] = tmp;
    }
  }
 
    ll l = 0, r = 10000000;
    while (r - l > 1) {
      ll med = (l + r) / 2;
      a[0] = med; b[0] = in - out + med;
      bool flag = true;
      rep(i, n) {
        if (a[i] > in + med - b[i]) {
            flag = false;
            break;
        }
      }
      if (flag) l = med;
      else r = med;
    }
    cout << r << endl;
  
  return 0;
}