#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int tt = 1;
//cin >> tt;
while(tt--) {
int n;
cin >> n;
vector<pair<long long, long long>> a(n);
for(int i = 0;i < n;i++)
cin >> a[i].f >> a[i].s;
sort(a.begin(), a.end());
vector<long long> d(n);
for(int i = 1;i < n;i++)
d[i] = a[i - 1].f - a[i].f + a[i].s;
vector<long long> dp(n);
long long ans = 0;
for(int i = n - 2;i >= 0;i--)
dp[i] = max(0ll, dp[i + 1] + d[i + 1]);
for(int i = 0;i < n;i++)
ans = max(ans, dp[i] + a[i].s);
cout << ans;
}
return 0;
}
