#include <bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define int long long
using namespace std;
///Constants
//int mod = 1000000007;
/*void setIO(string s)
{
freopen((s + ".in").c_str(), "r", stdin);
freopen((s + ".out").c_str(), "w", stdout);
}*/
int dp[500010];
signed main()
{
IOS;
memset(dp, -1, sizeof(dp));
int n, a, b;
cin >> n;
vector<pair<int, int>>v;
vector<int>pre;
v.push_back({0, 0});
for(int i = 0 ; i < n ; ++i){
cin >> a >> b;
v.push_back({a, b});
}
sort(v.begin(), v.end());
a = 0;
for(int i = 0 ; i <= n ; ++i){
a+=v[i].second;
pre.push_back(a);
}
int mx = -1;
for(int i = 0 ; i < 1 ; ++i){
for(int j = n ; j >= i+1 ; --j){
int lol = (pre[j]-pre[i])-(v[j].first-v[i+1].first);
mx = max(mx, lol);
//cout << i << " " << j << " " << lol << " "<< mx << "\n";
}
}
cout << mx ;
return 0;
}
