nyoj410 how many ones?

how many ones?

时间限制：3000 ms  |  内存限制：65535 KB

难度：2

描述

Given any integer 0 <= n <= 10000 not divisible by 2 or 5, some multiple of n is a number which in decimal notation is a sequence of 1's. How many digits are in the smallest such a multiple of n?

输入

Each line contains a number n.

输出

Output the number of digits.

样例输入

3 7 9901

样例输出

3612

来源

Waterloo local 2001.06.02

上传者

苗栋栋

/*悲剧，总是被叫做水题的基础题虐，，，基础差，死的难看。。。Time:2014-12-7 14:15*/#include<cstdio>#include<cstring>int main(){int sum,num;int n;while(scanf("%d",&n)!=EOF){sum=num=0;while(1){sum++;num=(num*10+1)%n;//如果是2或者5的话，找不着，每次对n取模，突然想起离散数学里边的知识的，就是忘了什么东东来着 貌似是循环群来吧 if(num==0) break;}printf("%d\n",sum); }return 0;}