#include <stdio.h>

double fun ( int n )

{ double result = 1.0 ;

/************found************/

  if( n = = 0)

    return 1.0 ;

  while( n >1 && n < 170 )

/************found************/

    result *= n--;

  return result ;

}

main ( )

{ int n ;

  printf("Input N:") ;

  scanf("%d", &n) ;

  printf("\n\n%d! =%lf\n\n", n, fun(n)) ;

}