#include <bits/stdc++.h>
#define rep(i,a,b) for(int i = (a);i <= (b);i++)
#define repd(i,a,b) for(int i = (a);i >= (b);i--)
#define PB push_back
#define F first
#define S second
#define Task ""
using namespace std;
template <class T> T read(T &a){ifstream cin (Task".inp");a = 0;char c = cin.get();bool nega = 0;while(!isdigit(c) && c != '-')c = cin.get();if(c == '-')nega = 1,c = cin.get();a = c - 48;c = cin.get();while(isdigit(c))a = a * 10 + c - 48,c = cin.get();if(nega)a = -a;return a;}
template <class T> void writep(T a){ofstream cout (Task".out");if(a > 9)writep(a / 10);cout.put(a % 10 + 48);}
template <class T> void write(T a){ofstream cout (Task".out");if(a < 0)cout.put('-'),a = -a;writep(a);cout.put(' ');}
template <class T> void writeln(T a){ofstream cout (Task".out");write(a);cout.put('\n');}
const int N = 500012;
int n;
pair<long long,long long> a[N];
int main()
{
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// ifstream cin (Task".inp");
// ofstream cout (Task".out");
cin >> n;
rep(i,1,n)
cin >> a[i].F >> a[i].S;
sort(a+1,a+n+1);
rep(i,1,n) a[i].S += a[i-1].S;
long long ans = 0;
rep(i,1,n)
{
rep(j,1,i)
ans = max(ans,a[i].S - a[j-1].S - a[i].F + a[j].F);
}
cout << ans;
return 0;
}
