#include<iostream>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<set>
#include<map>
#include<queue>
using namespace std;
typedef long long ll;
const int MOD=1e9+7;
int main() {
  int n,a[10000]={},b[10000]={},M,A=0,B=0,d;
  cin >> n;
  for(int i=0; i<n-1; i++) {
    cin >> a[i] >> b[i];
    A+=a[i],B+=b[i];
  }
  M=max(A,B);
  d=abs(A-B);
  cout << abs(M-d)+1 << endl;
}