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

int main() {
    int n;
    cin >> n;

    int maxInDeg = 0;
    int inSum = 0; // ->
    int outSum = 0; // <-
    for (int i = 0; i < n-1; ++i){
        int in, out;
        cin >> in >> out;
        inSum += in;
        outSum += out;
    }
    int ans = max(inSum, outSum) - abs(inSum - outSum) + 1;
    cout << ans << endl;
}