#include <bits/stdc++.h>
#define inf 2000000000000000000LL
#define N 500005
#define f first
#define s second
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pii;
ll n, resp, sum[N], a, b;
pii v[N];
int main()
{
ios::sync_with_stdio(false); cin.tie(0);
cin>>n;
for(int i = 1; i <= n; i++) cin>>v[i].f>>v[i].s;
sort(v + 1, v + n + 1);
for(int i = 1; i <= n; i++) sum[i] = sum[i - 1] + v[i].s;
ll melhor = -inf;
for(int i = 1; i <= n; i++)
{
melhor = max(melhor, -sum[i - 1] + v[i].f);
resp = max(resp, sum[i] - v[i].f + melhor);
}
cout<<resp<<"\n";
}
