// #pragma GCC optimize("O3")
// #pragma GCC optimization("Ofast,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define FOR(i, l, r) for (int i = (l); i <= (r); i++)
#define FOD(i, r, l) for (int i = (r); i >= (l); i--)
#define fi first
#define se second
#define pii pair<int, int>
const ll mod = 1e9 + 7;
const int MAXN = 5e5 + 5;
const ll oo = 1e18+7;
const int base = 0;
int n;
pii a[MAXN];
int ps[MAXN];
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// freopen("test.txt", "r", stdin);
// freopen("o2.out", "w", stdout);
// if(fopen(".inp", "r")){
// freopen(".inp", "r", stdin);
// freopen(".out", "w", stdout);
// }
cin >> n;
FOR(i, 1, n){
cin >> a[i].fi;
cin >> a[i].se;
}
sort(a+1, a+1+n);
FOR(i, 1, n){
ps[i]=ps[i-1]+a[i].se;
}
int mx=-oo, ans=-oo;
FOR(i, 1, n){
mx=max(mx, -ps[i-1]+a[i].fi);
ans=max(ans, ps[i]-a[i].fi+mx);
}
cout << ans;
return 0;
}
