#include<iostream.h>
#include<stdio.h>
FILE *f=fopen("energii.in","r"),*g=fopen("energii.out","w");
 int main()
{
long a[15000],b[15000],i,j,n,e,k=0,k1;
long min=5000000;
long s=0,s1=0;
fscanf(f,"%ld\n",&n);
fscanf(f,"%ld\n",&e);
 for(i=1;i<=n;i++)
{
fscanf(f,"%ld %ld\n",&a[i],&b[i]);
s+=a[i];
}
if(s<e) fprintf(g,"-1");
else
{
if(s==e)
{
s=0;
for(i=1;i<=n;i++)
s+=b[i];
fprintf(g,"%ld",s);
}
else
{
for(i=1;i<=n;i++)
{
k=i;
s=a[i];
s1=b[i];
while(k<=n)
{
k1=k;
if(k!=i)
{
s+=a[k];
s1+=b[k];
}
while(s<e&&k1<=n)
{
k1++;
s+=a[k1];
s1=s1+b[k1];
}
if(s1<min&&s>=e) min=s1;
k++;
}
}
}
fprintf(g,"%ld",min);
}
return 0;
}