HDU 2674 N！Again （数论-水题）

N！Again

Problem 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

 

Author

WhereIsHeroFrom

 

Source

HDU女生专场公开赛——谁说女子不如男

 

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题目大意：

求N!%2009的最大值，n最大10^9;

解题思路：

我靠，乍一看数据量挺大的，几秒后反应过来，n>=2009后还要计算个毛线。

解题代码：

#include <iostream>
#include <cstdio>
using namespace std;

int n;

int main(){
    while(scanf("%d",&n)!=EOF){
        if(n>=2009) printf("0\n");
        else{
            int ans=1;
            for(int i=2;i<=n;i++){
                ans=(ans*i)%2009;
            }
            printf("%d\n",ans);
        }
    }
    return 0;
}