#include <cstdio>
using namespace std;
long n,k,a,b,v[25002],i,max;
int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    scanf("%ld%ld",&n,&k);
    v[0]=1;
    for(max=1;max<=n;max++){
        scanf("%ld%ld",&a,&b);
        for(i=k-1;i>=0;i--){
            if((v[i])&&((v[i+a]>v[i]+b)||(v[i+a]==0))){v[i+a]=v[i]+b;}
                         }
                     }
    max=999999999;
    for(i=k;i<=25001;i++){if((v[i]<max)&&(v[i]!=0)){max=v[i];}}
    if(max<999999999){printf("%ld",max-1);}
    else{printf("-1");}
return 0;
}