//* --- ©ZeroCoolCorp --- *//
#include <bits/stdc++.h>
#define ll long long
using namespace std;
#define mxn int(1e5 + 5)
#define inf 1e9
#define log 19
#define int ll
//jiojkljljkjlk
void solve(){
int n;
cin>>n;
pair<int,int> A[n];
int dp[n];
for(int i = 0;i<n;i++){
cin>>A[i].first>>A[i].second;
dp[i] = 0;
}
sort(A,A+n);
dp[0] = A[0].second;
int mx = dp[0] + A[0].first;
int ans = -1;
for(int i = 1;i<n;i++){
dp[i] = max(A[i].second, mx + A[i].second - A[i].first);
mx = max(mx,dp[i] + A[i].first);
ans = max(ans,dp[i]);
}
cout<<ans<<endl;
}
int32_t main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
//cin>>t;
while(t--)solve();
}
