#include<stdio.h>


int main()
{
freopen("energii.in","rt",stdin);
freopen("energii.out","wt",stdout);
long n,m,i,nr,max = 2000000000;
long v[15001],c[1001],x[1001];
scanf("%ld%ld",&n,&m);
for(i=1;i<=n;i++)
scanf("%ld%ld",&x[i],&c[i]);

for(i=1;i<=m+10001;i++)
v[i] = 2000000000;

for( nr = 1; nr <= n; nr++)
for( i = m; i >= 0  ; i--)
if(v[i]<2000000000)
{
if(i+x[nr]>=m && v[i]+c[nr] <max) max=v[i]+c[nr];
else
if(v[i+x[nr]]>v[i]+c[nr]) 
v[i+x[nr]] = v[i]+c[nr];
}

if(max<2000000000) printf("%ld",max);
else printf("-1\n");


return 0;
}