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

using ll = long long int;

int main() {
    int n;
    cin >> n;
    vector<ll> a(n*2), b(n);
    for(int i=0;i<n*2;i++){
        cin >> a[i];
    }
    ll ans, sum = 0;
    for(int i=0;i<n;i++){
        b[i] = a[i*2]-a[i*2+1];
        sum += b[i];
    }
    ans = sum;
    for(int i=n-1;i>=0;i--){
        sum -= b[i]*2;
        ans = max(ans, sum);
    }
    cout << ans << endl;
    return 0;
}