#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int N;
cin >> N;
pair<int, int>A[N];
for(int i = 0; i < N; i++){
cin >> A[i].first >> A[i].second;
}
sort(A, A+N);
int B[N], P[N+1] = {0};
for(int i = 0; i < N; i++){
P[i+1] = P[i] + A[i].second;
}
for(int i = 0; i < N; i++){
B[i] = P[i] - A[i].first;
}
int ma = A[0].second;
priority_queue<int, vector<int>, greater<int>>C;
for(int i = 1; i < N; i++){
C.push(B[i-1]);
ma = max(ma, P[i+1]-C.top()-A[i].first);
}
cout << ma;
}
