package main

import "fmt"

func Factorial(x int) (result int) {
  if x == 0 {
    result = 1   
  } else {
    result = x * Factorial(x - 1)
  }
  return
}

func main() {  
    var i int = 15
    fmt.Printf("%d 的阶乘是 %d\n", i, Factorial(i))
}