#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
#define pb push_back
#define ff first
#define ss second
#define ii pair<int, int>
#define vi vector<int>
#define vii vector<pair<int, int>>
#define rep(i, a, b) for (int i = a; i <= b; i++)
const int INF = 4e18;
const int MOD = 1e9 + 7;
int n; const int mx = 5e5 + 3;
ii a[mx]; int pfs[mx];
int ans = -INF;
void GetInput() {
cin >> n;
rep(i, 1, n) cin >> a[i].ff >> a[i].ss;
}
void Solve() {
sort(a+1, a+1+n);
rep(i, 1, n) pfs[i] = pfs[i-1] + a[i].ss;
int ma = a[1].ff;
rep(i, 1, n) {
ma = max(ma, a[i].ff - pfs[i-1]);
ans = max(ans, pfs[i] - a[i].ff + ma);
}
}
void PrintAns() {
cout << ans;
}
void Reset() {
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
int TEST = 1;
//cin >> TEST;
while (TEST--) {
Reset();
GetInput();
Solve();
PrintAns();
}
return 0;
}
