#include <bits/stdc++.h>
#define int long long
#define N 500001
using namespace std;
const int inf=1e18;
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n;
cin >> n;
int a[n+1],b[n+1];
vector<pair<int,int>> v(n+1);
for(int i=1;i<=n;i++){
cin >> a[i] >> b[i];
v[i].first=a[i];
v[i].second=b[i];
}
sort(v.begin(),v.end());
for(int i=1;i<=n;i++){
a[i]=v[i].first;
b[i]=v[i].second;
}
/*
for(int i=1;i<=n;i++){
cout << a[i] << " " << b[i] << "\n";
}
*/
int dp[N][2];
memset(dp,0,sizeof(dp));
int ans=-inf;
for(int i=1;i<=n;i++){
dp[i][1]=max(dp[i][1],dp[i-1][0]+a[i]+b[i]);
dp[i][1]=max(dp[i][1],dp[i-1][1]+b[i]);
ans=max(ans,dp[i][1]-a[i]);
}
cout << ans << "\n";
return 0;
}
