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

int main() {

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

    return 0;
}