//IN THE NAME OF GOD
#include<bits/stdc++.h>
#pragma GCC optimize("O2,unroll-loops")
#define endl '\n'
#define F first
#define S second
using namespace std;
typedef long long ll;
typedef long double dll;
ll N = 5e5+7;
vector<pair<ll,ll>> v, hav;
int32_t main(){
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ll n; cin >> n;
for(ll i=1; i<=n; i++){
ll a,b; cin >> a >> b;
v.push_back({a,b});
}
sort(v.begin(),v.end());
hav.push_back(v[0]);
for(ll i=1; i<n; i++){
if (v[i].F == hav.back().F) hav.back().S += v[i].S;
else hav.push_back(v[i]);
}
ll ans = 0, tmp = 0;
for(ll i=ll(hav.size())-1; i>=0; i--){
ans = max(ans, hav[i].S);
if (i == int(hav.size())-1) tmp = hav[i].S;
else tmp = max(hav[i].S,tmp+hav[i].S-hav[i+1].F+hav[i].F);
ans = max(ans, tmp);
}
cout << ans << endl;
return 0;
}
