hdu--2674

Description

WhereIsHeroFrom:             Zty, what are you doing ? 
Zty:                                     I want to calculate N!...... 
WhereIsHeroFrom:             So easy! How big N is ? 
Zty:                                    1 <=N <=1000000000000000000000000000000000000000000000… 
WhereIsHeroFrom:             Oh! You must be crazy! Are you Fa Shao? 
Zty:                                     No. I haven's finished my saying. I just said I want to calculate N! mod 2009 


Hint : 0! = 1, N! = N*(N-1)! 

 

Input

Each line will contain one integer N(0 <= N<=10^9). Process to end of file. 

 

Output

For each case, output N! mod 2009 

 

Sample Input

     
     
     
     

      
      
      
      4 
5 
     
     
     
     

 

Sample Output

     
     
     
     

      
      
      
      24
120 
     
     
     
     

 

解体思路：（1*2*3*4..............*n)%2009=((.....((1%2009)*2)%2009.....)*n)%2009;又2009=7*7*41，所以比41大的数结果都为0；问题缩小到了41。接下来处理问题就变得简单多了。

代码如下：

#include<stdio.h>
#include<string.h>
int main(){
	long long n,m;
	while(scanf("%lld",&n)!=EOF){
		if(n>=41){
			printf("0\n");
            continue;
		}
		else if(n==0){
			printf("1\n");
		}
		else {
			m=1;
			for(int i=1;i<=n;i++){
				m=(m*i)%2009;
			}
			printf("%d\n",m%2009);
		}
	}
	return 0;
}