#include<bits/stdc++.h>
#define fi first
#define se second
#define lld long long
#define LINF 1000000000000000000LL
using namespace std;
#define MAXN 500010
pair<lld, lld> p[MAXN];
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int N; cin >> N;
for(int i = 1; i <= N; i++) cin >> p[i].fi >> p[i].se;
sort(p+1, p+1+N);
lld sum = 0;
lld maxx = -LINF;
lld rez = -LINF;
for(int i = 1; i <= N; i++) {
maxx = max(maxx, p[i].fi - sum);
sum += p[i].se;
rez = max(rez, maxx + sum - p[i].fi);
}
cout << rez;
}
