#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define F first
#define S second
const int maxn = 1e6+10;
const int mod = 1e9+7;
int n, k;
ll a[maxn], b[maxn], pre[maxn];
vector<pair<ll,ll>> ve;
int main()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>> n;
for(int i = 1; i <= n; i++){
cin>> a[i] >> b[i];
ve.push_back({a[i],b[i]});
}
sort(ve.begin(), ve.end());
ll mx = 0, ans = 0;
for(int i = 0; i < n; i++)
{
pre[i] = pre[i-1] + ve[i].S;
mx = max(mx, ve[i].F - pre[i-1]);
ans = max(ans, pre[i] - ve[i].F + mx);
}
cout<< ans;
}
