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;
}