#include<iostream>
#include<cstdio>
#define INF 0x3f3f3f3f
using namespace std;
int e[1005],c[1005],v[15005],g,w,n,i,j,sol;
int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    scanf("%d%d",&g,&w);
    for(i=1; i<=g; ++i)
        scanf("%d%d",&e[i],&c[i]);
    n=15000;
    for(i=1; i<=n; ++i)
        v[i]=INF;
    for(i=1; i<=g; ++i)
    {
        for(j=n-e[i]; j>=0; --j)
            if(v[j+e[i]]>v[j]+c[i])
                v[j+e[i]]=v[j]+c[i];
    }
    sol=INF;
    for(i=w; i<n; ++i)
        if(v[i]<sol) sol=v[i];
    if(sol==INF) sol=-1;
    printf("%d\n",sol);
    return 0;
}