#include <stdio.h>
#define INF 12128
int v[5128];
int main()
{int a,b,i,n,w,rez,j;
freopen("energii.in","r",stdin);
freopen("energii.out","w",stdout);
scanf("%d%d", &n, &w);
for(i=1;i<=w;i++)
v[i]=INF;rez=INF;
for(i=1;i<=n;i++)
{scanf("%d%d", &a, &b);
if(a>=w){if(b<rez) rez=b;}
else {for(j=w-a;j<=w;j++)
if(v[j]+b<rez) 
rez=v[j]+b;
for(j=w-a;j>=0;j--)
if(v[j]+b<v[j+a]) 
v[j+a]=v[j]+b;
}}	if (rez!=INF) 
printf("%d\n",rez);
else 
printf("-1\n");
}