#include <bits/stdc++.h>

#define int long long
using namespace std;
const int MAXN = 50010;
pair<int, int> P[MAXN];

signed main() {
    //freopen("in", "r", stdin);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    for (int i = 1; i <= N; i++) {
        cin >> P[i].first >> P[i].second;
        P[i].first += P[i].second;
    }
    sort(P + 1, P + 1 + N);
    int ans = -0x3f3f3f3f, sum;
    for (int i = 1; i <= N; i++) {
        sum -= P[i].second;
        ans = max(ans, sum);
        sum +=P[i].first;
    }
    cout << ans << endl;
    return 0;
}