#include <iostream>
#include <fstream>
using namespace std;

int main()
{int n,m,ok,mini,v[100],a[100],i,on;
ifstream f("energii.in");
ofstream g("energii.out");
f>>n>>m;
for(i=1;i<=n;i++)
{
    f>>v[i];
    f>>a[i];
}
ok=0;
i=1;
while((ok==0)&&(i<=n))
{
    if(v[i]>=mini)
    {
        mini=a[i];
        ok=1;
    }
    i++;
}
on=0;
for(i=1;i<=n;i++)
{
    if(v[i]>=m)
    {
        if(mini<=a[i])
        {
            mini=a[i];
            on=1;
        }
    }
}
if(on==1)
{
    g<<mini;
}
else
{
    g<<"-1";
}
    return 0;
}