#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define F first
#define S second
#define MAXN 200010
const int INF = 1e18;
const int MOD = 1e9+7;
void solve(){
int n; cin >> n;
vector<pair<int, int>> a(n);
for(auto&[f, s]: a) cin >> f >> s;
sort(a.begin(), a.end());
int mx = 0, sum = 0, mn = INF;
for(auto&[x, y]: a){
mn = min(mn, sum-x);
sum += y;
mx = max(mx, sum-x-mn);
}
cout << mx;
}
signed main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int t = 1; //cin >> t;
while(t--) solve();
return 0;
}
