static boolean isReachable ( int sx , int sy , int dx , int dy ) {
  if ( sx > dx || sy > dy ) return false ;
  if ( sx == dx && sy == dy ) return true ;
  return ( isReachable ( sx + sy , sy , dx , dy ) || isReachable ( sx , sy + sx , dx , dy ) ) ;
}

static boolean isReachable ( int sx , int sy , int dx , int dy ) { if ( sx > dx || sy > dy ) return false ; if ( sx == dx && sy == dy ) return true ; return ( isReachable ( sx + sy , sy , dx , dy ) || isReachable ( sx , sy + sx , dx , dy ) ) ; }
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