#include <bits/stdc++.h>
#define IO ios::sync_with_stdio(false);cin.tie(0);
#define debug(x) cerr << #x << " = " << (x) << ' '
#define bug(x) cerr << (x) << ' '
#define endl cerr << '\n'
#define all(v) (v).begin(), (v).end()
#define SZ(v) (ll)(v).size()
#define lowbit(x) (x)&-(x)
#define pb emplace_back
#define F first
#define S second
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
//#define TEST
const int N = 5e5+5;
pll a[N];
int main(void)
{ IO
int n, i;
cin >> n;
for (i=1; i <= n; ++i) cin >> a[i].F >> a[i].S;
ll ans = 0, sum = 0, mx = -2e18;
sort(a+1, a+n+1);
for (i=1; i <= n; ++i)
{
mx = max(mx, -sum + a[i].F);
sum += a[i].S;
ans = max(ans, sum + mx - a[i].F);
}
cout << ans << '\n';
return 0;
}
