#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] = {0};
B[0] = A[0].second;
for(int i = 1; i < N; i++){
B[i] = A[i].second - A[i].first + A[i-1].first;
}
int c = 0, m = 0, j = 0;
while (j < N-1 && A[j].second - A[j+1].first + A[j].first < 0){
j++;
}
c = A[j].second;
m = max(c, m);
for(int i = j+1; i < N; i++){
c += B[i];
if (c < 0) c = A[i].second;
m = max(c, m);
}
cout << m;
}
