// File artexhibition.cpp created on 02.10.2025 at 19:25:28
#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "/home/ahmetalp/Desktop/Workplace/debug.h"
#else
#define debug(...) void(23)
#endif
constexpr i64 inf = i64(1E18);
template<typename T>
bool chmax(T& a, T b) {
if (a < b) {
a = b;
return true;
}
return false;
}
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int N;
std::cin >> N;
std::vector<std::array<i64, 2>> A(N);
for (int i = 0; i < N; ++i) {
std::cin >> A[i][0] >> A[i][1];
}
std::sort(A.begin(), A.end());
i64 ans = 0, x = -inf, sum = 0;
for (int i = 0; i < N; ++i) {
chmax(x, -sum + A[i][0]);
sum += A[i][1];
chmax(ans, sum + x - A[i][0]);
}
std::cout << ans << '\n';
return 0;
}
