#include "bits/stdc++.h"
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
using ll=long long;
constexpr ll INF = 1e18, mod = 1e9 + 7, N = 2e5 + 5;
void solve(){
ll n,m;
cin >> n;
vector<pair<ll,ll>>v;
v.push_back({0ll, 0ll});
ll a,b;
for(int i = 0; i < n; i++){
cin >> a >> b;
v.push_back({a,b});
}
sort(v.begin(),v.end());
ll maxi = 0;
ll cur = 0;
for(int i = 1; i <= n; i++){
cur += v[i].second;
cur = max(cur, v[i].first + v[i].second);
maxi = max(maxi, cur - v[i].first);
}
cout << maxi << endl;
}
int main() {
fast;
ll t = 1;
// cin >> t;
while(t--){
solve();
}
return 0;
}
