#include <bits/stdc++.h>

using namespace std;

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

int dp[1005][10005] ;
int e[1005] , c[1005] ;

int main()
{
    int i , j , g , w ;
    fin >> g >> w ;
    for ( i = 1 ; i <= g ; i++ )
    {
        fin >> e[i] >> c[i] ;
        dp[1][e[i]] = c[i] ;
    }
    for ( i = 2 ; i <= g ; i++ )
    {
        for ( j = 1 ; j <= w ; j++ )
        {
            dp[i][j] = dp[i-1][j] ;
            if ( j-e[i] >= 0 && dp[i-1][j-e[i]] != 0 )
                dp[i][j] = min(dp[i][j],dp[i-1][j-e[i]] + c[i]) ;
        }
    }
    fout << dp[g][w] ;
}