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

using ll=long long;

int main(){
    int N;
    cin>>N;
    int sumA=0,sumB=0;
    for(int i=0;i<N-1;i++){
        int A,B;
        cin>>A>>B;
        sumA+=A,sumB+=B;
    }
    if(sumA>=sumB){
        cout<<sumA-(sumA-sumB)+1<<endl;
    }else{
        cout<<sumB-(sumB-sumA)+1<<endl;
    }
    return 0;
}