#include <bits/stdc++.h>
#define fi first
#define se second
#define lc id<<1
#define rc id<<1^1
#define nmax 500008
const long long inf = 1e18;
using namespace std;
typedef pair<long long, long long> pii;
int n;
pii a[nmax];
long long ans = -1, pre = inf, f[nmax];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 1; i <= n; i++)
cin >> a[i].fi >> a[i].se;
sort(a + 1, a + n + 1);
for (int i = 1; i <= n; i++){
f[i] = f[i - 1] + a[i].se;
ans = max(ans, f[i] - a[i].fi - pre);
pre = min(pre, f[i - 1] - a[i].fi);
}
cout << ans;
return 0;
}
