#include<bits/stdc++.h>
using namespace std;
#define X first
#define Y second
const int N = 2002;
const int inf = 2e9 + 7;
typedef pair<int,int> ii;
int f[N][N];
ii rope[N];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
for(int i = 1 ; i <= n ; ++i) {
cin >> rope[i].X;
cin >> rope[i].Y;
}
sort(rope + 1, rope + 1 + n,greater<ii>());
for(int i = n ; i >= 1 ; --i)
for(int j = 0 ; j <= n ; ++j) {
if (i > n) {
f[i][j] = 0;
continue;
}
f[i][j] = max(f[i + 1][j],j > 0 ? f[i + 1][min(j - 1 + rope[i].X,n)] + rope[i].Y : 0);
}
cout << f[1][1] << endl;
}
