#include <iostream>
using namespace std;
int
father[101], x, y, recordf[101], fcnt;
void
__read__()
{
cin >> x >> y;
int
a, b;
while( cin >> a >> b )
father[a] = b;
}
void
__recordf__( int f )
{
if( f != 0 )
{
recordf[f] = true;
__recordf__( father[f] );
}
}
void
__find__( int x )
{
if( recordf[x] )
{
cout << x << endl;
return;
}
else if( x != 0 )
__find__( father[x] );
}
int
main()
{
__read__();
__recordf__( x );
__find__( y );
return 0;
}