#include <bits/stdc++.h>

using namespace std;


ifstream fin ("credite.in");
ofstream fout ("credite.out");


int dp[2][10005] , n;


struct D
{
    int val , timp;
};

D a[10005];


inline bool CMP(const D A , const D B)
{
    return A . timp < B . timp;
}


int main()
{
    int lin = 0 , mx = 0;
    fin >> n;
    for(int i = 1 ; i <= n ; i++)
        fin >> a[i] . val >> a[i] . timp;
    sort(a + 1 , a + n + 1 , CMP);
    for(int i = 1 ; i <= n ; i++)
    {
        lin = 1 - lin;
        for(int j = 1 ; j <= a[i] . timp ; j++)
            dp[lin][j] = max(dp[1 - lin][j - 1] + a[i] . val , dp[1 - lin][j]);
    }
     mx = 0;
    for(int i = 1 ; i <= a[n] . timp ; i++)
        mx = max(mx , dp[lin][i]);
    fout << mx << "\n";
    fin.close();
    fout.close();
    return 0;
}