#include <bits/stdc++.h>
using namespace std;
#define int long long
const int inf = 1e18 + 7;
const int MOD = 1000000007;
const int MOD1 = 998244353;
const int MOD2 = 1e9 + 9;
const int MAXXX = 1e3 + 5;
const int MAXXXx = 1e3 + 5;
const int OFFSET = 200;
void Make_set(vector<int>& v)
{
set<int> s(v.begin(), v.end());
v.assign(s.begin(), s.end());
}
int Pow(int n, int k, int mod)
{
int res = 1;
while (k > 0)
{
if (k % 2 == 1)
{
res = (res * n) % mod;
}
n = (n * n) % mod;
k /= 2;
}
return res;
}
vector<pair<int, vector<int>>> dp(MAXXX);
int x[MAXXX];
signed main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
int T ;
// cin >> T;
T = 1;
for (int K = 0; K < T; K++)
{
int n;
cin >> n;
int a[n], b[n];
for(int i = 0; i < n; i++) cin >> a[i] >> b[i];
int pr[n], ans = 0, mn = inf;
sort(a, a + n);
pr[0] = a[0];
for(int i = 1; i < n; i++)
{
pr[i] = pr[i - 1] + a[i];
}
for(int r = 0; r < n; r++)
{
ans = max(ans , pr[r] - a[r] - mn);
mn = min(mn, pr[r] - a[r]);
}
cout << ans;
}
return 0;
}
