N！Again（数论）

N！Again

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3885    Accepted Submission(s): 2080

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

24120

 

Author

WhereIsHeroFrom

 

阶乘求余问题！这里为什么41以及41之后就为0了呢？

因为N=40，结果为245，N=41时，结果为

245*41=10045%2009=0。

#include<cstdio>#include<cstring>#include<iostream>using namespace std;int main(){    int n,ans,i;    while(cin>>n)    {        ans=1;        if(n>=2009)        {            cout<<"0"<<endl;        }        else        {            for(i=1;i<=n;i++)            {                ans*=i;                ans%=2009;            }            cout<<ans<<endl;        }    }}