#include<bits/stdc++.h>
#define ll long long
#define endl "\n"
#define fi first
#define se second
#define pb push_back
#define pll pair<long long, long long>
#define loop(i,n) for(int i=1;i<=n;i++)
#define loop0(i,n) for(int i=0;i<n;i++)
using namespace std;
//pbds template
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//template <class T>
//using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
void solve(){
ll n;
cin >> n;
map<ll,ll> mp;
for(int i=1;i<=n;i++){
ll a,b;
cin >> a >> b;
mp[a] += b;
}
ll ans = 0;
ll prev = -1;
ll temp = 0;
for(auto i:mp){
ll selisih = i.fi-prev;
// cout << temp << ' ' << selisih << endl;
if(temp<selisih){
temp = 0;
}
else{
temp -= selisih;
}
// cout << i.fi << ' ' << temp << ' ' << selisih << ' ' << i.se << ' ' << ans << endl;
ans = max(ans, temp+i.se);
temp += i.se;
prev = i.fi;
}
cout << ans << endl;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int tc = 1;
// cin >> tc;
while(tc--){
solve();
}
}
