POJ 2773 Happy 2006

Happy 2006

Time Limit: 3000MS Memory Limit: 65536KTotal Submissions: 11832 Accepted: 4183

Description

Two positive integers are said to be relatively prime to each other if the Great Common Divisor (GCD) is 1. For instance, 1, 3, 5, 7, 9...are all relatively prime to 2006. 

Now your job is easy: for the given integer m, find the K-th element which is relatively prime to m when these elements are sorted in ascending order. 

Input

The input contains multiple test cases. For each test case, it contains two integers m (1 <= m <= 1000000), K (1 <= K <= 100000000).

Output

Output the K-th element in a single line.

Sample Input

2006 12006 22006 3

Sample Output

135

题意是找与m互质的第k大的数。
首先枚举比m小的与m互质的个数，然后从前往后面找规律。举例 4:1是 2不是 3是 4不是。所以能够推出后面以4为
单位的数字里面也一定是这个关系 是 不是 是 不是。
这样通过求余就能够找到是第几个了。

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;int prime[1000005];int gcd(int a,int b){    return b==0?a:gcd(b,a%b);}int main(){    int m,k;    while(scanf("%d%d",&m,&k)!=EOF)    {        int t=0;        for(int i=1;i<=m;i++)        {            if(gcd(i,m)==1)                prime[t++]=i;        }        if(k%t!=0)            printf("%d\n",k/t*m+prime[k%t-1]);        else printf("%d\n",(k/t-1)*m+prime[t-1]);    }    return 0;}