/*
   Keep it Simple!
*/

#include<stdio.h>

#define MaxN 1005
#define MaxS 10055
#define inf 10060
#define MinV(a,b) (a<b?a:b)

long long OverAllMinV;
long long SumV;

int G,W;
int E[MaxN],C[MaxN];
int Mat[MaxS];



int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);

    scanf("%d%d",&G,&W);
    OverAllMinV = inf;

    for(int i=1; i<=G; i++)
    {
        scanf("%d%d",&E[i],&C[i]);
        SumV+=E[i];
    }

      for(int j=1;j<=SumV;j++)
        Mat[j] = inf;

     for(int i=1;i<=G;i++)
       for(int j=SumV; j>=1; j--)
               {
                 if(E[i] <= j)
                   Mat[j] = MinV(Mat[j-E[i]]+C[i],Mat[j]);
                 if(j>=W && OverAllMinV>Mat[j])
                    OverAllMinV = Mat[j];
               }

    printf("%d",OverAllMinV);

}