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

int main(){
    int N;
    cin >> N;
    vector<int64_t> A(N);
    for(int i=0; i<N; i++){
        int a, b;
        cin >> a >> b;
        A[i] = a-b;
    }
    int64_t sum = accumulate(A.begin(), A.end(), 0LL);
    int64_t ans = sum;
    for(int i=N-1; i>=0; i--){
        sum -= 2*A[i];
        ans = max(ans, sum);
    }
    cout << ans << endl;
    return 0;
}