#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 1e18;
typedef pair<int, int> pii;
#define fi first
#define se second
signed main(){
ios_base::sync_with_stdio(0); cin.tie(0);
int n;
cin >> n;
pii a[n];
for(int i=0, ai, bi; i<n; i++){
cin >> ai >> bi;
a[i] = {ai, bi};
}
sort(a, a+n);
int pp[n+1];
auto p = pp+1;
p[-1] = 0;
int ans = 0;
int m = INF;
for(int i=0; i<n; i++){
auto [ai, bi] = a[i];
ans = max(ans, bi);
int cv = bi;
int cd = 0;
if(i){
cd = ai - a[i-1].fi;
}
p[i] = p[i-1] + cv - cd;
ans = max(ans, p[i] - m);
m = min(m, p[i] - cv);
}
cout << ans;
return 0;
}
