/*
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O3")
#pragma GCC target ("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
*/
#include<bits/stdc++.h>
#define sz(v) (int)v.size()
#define ll long long
#define pb push_back
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define nl "\n"
using namespace std;
const int N = (int)5e5 + 7; // make sure this is right
const int M = (int)1e3 + 7;
const int inf = (int)2e9 + 7;
const ll INF = (ll)3e18 + 7;
const ll MOD = (ll)1e9 + 7; // make sure this is right
bool bit(int x, int i) {
return x >> i & 1;
}
int sum(int x, int y) {
x += y;
if(x >= MOD) x -= MOD;
return x;
}
int n;
pair<ll, int> a[N];
ll p[N];
void solve() {
cin >> n;
for(int i = 1; i <= n; ++i) {
cin >> a[i].x >> a[i].y;
}
sort(a + 1, a + 1 + n);
for(int i = 1; i <= n; ++i) {
p[i] = p[i - 1] + a[i].y;
}
ll ans = 0, cur = -INF;
for(int i = 1; i <= n; ++i) {
cur = max(cur, a[i].x - p[i - 1]);
ans = max(ans, p[i] - a[i].x + cur);
}
cout << ans << "\n";
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
int test = 1;
//cin >> test;
for(int i = 1; i <= test; ++i) {
//cout << "Case #" << i << ": ";
solve();
}
return 0;
}
