public static long repeatedProduct ( long n ) {
  long prod = 1 ;
  while ( n > 0 || prod > 9 ) {
    if ( n == 0 ) {
      n = prod ;
      prod = 1 ;
    }
    prod *= n % 10 ;
    n /= 10 ;
  }
  return prod ;
}

public static long repeatedProduct ( long n ) { long prod = 1 ; while ( n > 0 || prod > 9 ) { if ( n == 0 ) { n = prod ; prod = 1 ; } prod *= n % 10 ; n /= 10 ; } return prod ; }
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