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

24120 

 

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;}