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

#define CIN( LL , A ) LL A; cin >> A 
#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 , B_1 );
  assert( 1 <= B_1 && B_1 <= 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 , 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 A[2][2];
  int B[2] = { B_0 , B_1 };
  int i_0 = ( B_0 >= B_1 ? 0 : 1 );
  int i_1 = 1 - i_0;
  A[i_0][i_0] = 1;
  A[i_0][i_1] = 0;
  A[i_1][i_0] = 0;
  A[i_1][i_1] = 1;
  int q;
  while( B[i_1] != 0 ){
    q = B[i_0] / B[i_1];
    A[i_0][i_0] -= q * A[i_1][i_0];
    A[i_0][i_1] -= q * A[i_1][i_1];
    B[i_0] %= B[i_1];
    swap( i_0 , i_1 );
  }
  int gcd = B[i_0];
  int c = C_0 % gcd;
  if( C_1 % gcd != c ){
    RETURN( "NaN" );
  }
  int lcm = ( B_0 / gcd ) * B_1;
  int answer = c + A[i_0][0] * B_0 * ( ( C_1 - c ) / gcd ) + A[i_0][1] * B_1 * ( ( C_0 - c ) / gcd );
  answer = ( answer >= 0 ? answer % lcm : ( lcm - ( -answer ) % lcm ) % lcm );
  RETURN( answer );
}