#include <iostream>
#include <string>
#include <stdio.h>
#include <stdint.h>
using namespace std;

#define CIN( LL , A ) LL A; cin >> A 
#define TYPE_OF( VAR ) remove_const<remove_reference<decltype( VAR )>::type >::type
#define FOR( VAR , INITIAL , FINAL_PLUS_ONE ) for( TYPE_OF( FINAL_PLUS_ONE ) VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) 
#define QUIT return 0 
#define RETURN( ANSWER ) cout << ( ANSWER ) << "\n"; QUIT 
#include <cassert>

#define MAIN main

int MAIN()
{
  CIN( int , B_0 );
  assert( 1 <= B_0 && B_0 <= 100 );
  CIN( int , C_0 );
  assert( -100 <= C_0 && C_0 <= 100 );
  C_0 = ( C_0 >= 0 ? C_0 % B_0 : ( B_0 - ( - C_0 ) % B_0 ) % B_0 );
  CIN( int , B_1 );
  assert( 1 <= B_1 && B_1 <= 100 );
  CIN( int , C_1 );
  assert( -100 <= C_1 && C_1 <= 100 );
  C_1 = ( C_1 >= 0 ? C_1 % B_1 : ( B_1 - ( - C_1 ) % B_1 ) % B_1 );
  int product = B_0 * B_1;
  FOR( n , 0 , product ){
    if( n % B_0 == C_0 && n % B_1 == C_1 ){
      RETURN( n );
    }
  }
  RETURN( "NaN" );
}