#include<bits/stdc++.h>
using namespace std;
int main() {
    int N,a,b,A=0,B=0,M=0;
    cin>>N;
    while(cin>>a>>b)A+=a,B+=b,M=max(M,a+b);
    cout<<max(0,B-max({0,B-A,M-A})+1)<<endl;
}