# include <stdio.h>
int s,n,min,a[10005],b[10005],i,j,s1,s2,smin;
int main ()
{
freopen ("energii.in","r",stdin);
freopen ("energii.out","w",stdout);
scanf ("%li",&n);
scanf ("%li",&min);
for (i=1;i<=n;i++)
{
scanf ("%i",&a[i]);
scanf ("%i",&b[i]);
}
smin=30000000;
for (i=1;i<=n;i++)
{
s1=0;
s2=0;
for (j=i;j<=n;j++)
{
s1=s1+a[j];
s2=s2+b[j];
if (s1>=min)
if (s2<smin)
smin=s2;
}
}
printf ("%i",smin);
return 0;
}