#include <fstream.h>
#include <math.h>
int main ()
{long long n,m,i,x,y,min;
ifstream q ("energii.in");
ofstream w ("energii.out");
q>>n>>m;
min=LONG_MAX;
for(i=1;i<=n;i++)
	{q>>x>>y;
	if(x>=m && y<min)
		min=y;
	}
if(min==LONG_MAX)
	w<<-1<<'\n';
else
	w<<min<<'\n';
q.close ();
w.close ();
return 0;
}