#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    // max: A = sum(B), B = sum(A)
    // min: A = 0, B = sum(A) - sum(B)
    int N; cin >> N; N--;
    vector<int> A(N), B(N);
    int sumB = 0;
    rep(i,N) cin >> A[i] >> B[i], sumB += B[i];
    cout << sumB + 1 << endl;
}