//#pragma GCC target ("avx2")
//#pragma GCC optimize ("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define F first
#define S second
#define pb push_back
const int N = 1e6, NN=26;
const int mod=1e9+7;
//int gcd(int a, int b) { if (b == 0) return a; else return gcd(b, a % b); }
//int lcm(int a, int b) { return a / gcd(a, b) * b; }
//int binpow(int a,int b){if(!b)return 1; if(b&1)return a*binpow(a,b-1)%mod; int x=binpow(a,b/2); return x*x%mod;}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
pair < int, int > a[n+1];
int p[n+1]{};
for(int i=1;i<=n;i++) cin >> a[i].F >> a[i].S;
sort(a+1, a+n+1);
for(int i=1;i<=n;i++) p[i]=p[i-1]+a[i].S;
int sum=0, mn=-1e18, ans=0;
for(int i=1;i<=n;i++){
mn=max(mn, a[i].F-p[i-1]);
ans=max(ans, p[i]-a[i].F+mn);
}
cout << ans;
}
