#include <iostream>
#include <fstream>
#define gmax 1002
#define wmax 5002
using namespace std;

int dp[gmax][wmax],w[gmax],c[gmax],G,W;

int main()
{
    ifstream fin ("energii.in");
    ofstream fout("energii.out");
    fin>>G>>W;
    for(int i=1; i<=G; i++)
        fin>>w[i]>>c[i];
    for(int i=1; i<=G; i++)
    {
        for(int j=1; j<=W; j++)
        {
                dp[i][j]=dp[i-1][j];
                if(j>=w[i])
                    dp[i][j]=min(dp[i][j],dp[i-1][j-w[i]]+c[i]);
                if(dp[i][j]==0&&j>=w[i])
                        dp[i][j]=dp[i][j-w[i]]+c[i];
        }
    }
    fout<<dp[G][W];
    return 0;
}