main.cpp

易学c++源码

#include "iostream.h"
int isFactorial(long a);
void main()
{
	long temp;
	cin >>temp;
	cout <<isFactorial(temp) <<endl;
}
int isFactorial(long a)
{
	int i=1;
	long result=1;
	while (result<a)
	{	
		i++;
		result=result*i;
	}
	if (result==a)
	{
		return i;
	}
	else
	{
		return -1;
	}
}