#include <bits/stdc++.h>

using namespace std;

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

int g, w;
int dp[2][5005];

int main()
{
    int L = 1;
    fin >> g >> w;
    for(int i = 0; i <= 1; i ++)
    {
        for(int j = 1; j <= w;j ++)
        {
            dp[i][j] = 1e9;
        }
    }
    for(int i = 1; i <= g; i ++, L = 1 - L)
    {
        int e, c;
        fin >>  e >> c;
        for(int j = 1; j <= w; j ++)
        {
            dp[L][j] = dp[1 - L][j];
            if(j >= e)
            {
                dp[L][j] = min(dp[L][j], dp[1 - L][j - e] + c);
            }
            else
            {
                dp[L][j] = min(dp[L][j], c);
            }
        }
    }
    L = 1 - L;
    fout << dp[L][w];
    return 0;
}