#include<fstream.h>
#include<values.h>

long i,a[1002],b[1002],min,mins,sx,sy,s,m,ss,j,n;

int main()
{
ifstream f("energii.in");
ofstream g("energii.out");
f>>n>>m;
min=MAXLONG;
mins=MAXLONG;
for (i=1;i<=n;i++)
    {
    f>>a[i]>>b[i];
    sx+=a[i];sy+=b[i];
    }
if (sx<m) g<<-1<<'\n';
else if (sx==m) g<<sy<<'\n';
else {
for (i=1;i<=n;i++)
    {
    s=0;ss=0;
    for (j=i;j<=n;j++)
        {
        s+=a[j];ss+=b[j];
        if (s==m && ss<=mins) { mins=ss;break;}
        else if (s>m&&ss<=mins) {mins=ss;break;}
        }
    }
g<<mins<<'\n';
}
g.close();
return 0;
}