#include <stdio.h>
#include <algorithm>
using namespace std;
int n,e,energie[1001],cost[1001],x[2][1001];
int main(){
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    scanf("%d%d",&n,&e);
    for(int i=1;i<=n;++i)
        scanf("%d%d",&energie[i],&cost[i]);
    int ln=0,s=0;
    for(int i=1;i<=n;++i, ln=1-ln){
       s+=energie[i];
       for(int j=0;j<=e;++j){
            x[ln][j]=x[1-ln][j];
            if(j<=energie[i]){
                if(x[ln][j]==0)
                    x[ln][j]=cost[i];
                else
                    x[ln][j]=min(x[ln][j],cost[i]);
            }
            else if(s>=j){
                if(x[ln][j]==0)
                    x[ln][j]=x[1-ln][j-energie[i]]+cost[i];
                else
                    x[ln][j]=min(x[ln][j],x[1-ln][j-energie[i]]+cost[i]);
            }
            else
                break;

       }
    }
    if(x[1-ln][e]!=0)
        printf("%d",x[1-ln][e]);
    else
        printf("%d",-1);
    return 0;
}