#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
using pii = pair<i64, i64>;
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,avx2,mmx,fma,avx,tune=native")
const int N = 500'000, inf = 1'000'000'000;
const i64 infl = 1'000'000'000'000'000'000;
const int mod1 = 1'000'000'009, mod2 = 998'244'353;
const int p1 = 31, p2 = 37;
#define ff first
#define ss second
#define pb push_back
#define ins insert
#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define NO cout << "NO\n"
#define YES cout << "YES\n"
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int __tc = 1;
int n;
i64 ans = -infl * 2;
array<i64,2>a[N+5];
bool cmp(const array<i64,2>&x, const array<i64,2>&y) {
return x[0] < y[0];
}
void solve() {
sort(a + 1, a + n + 1, cmp);
for (int i = 1; i <= n; i++) {
i64 s = 0;
for (int j = i; j <= n; j++) {
s += a[j][1];
ans = max(ans, s - a[j][0] + a[i][0]);
}
}
cout << ans;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
// cin >> __tc;
for (int _tc = 1; _tc <= __tc; _tc++) {
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i][0] >> a[i][1];
solve();
}
}
