HDU 5597 GTW likes function 欧拉函数

题目链接：

http://acm.hdu.edu.cn/showproblem.php?pid=5597

题意：

http://bestcoder.hdu.edu.cn/contests/contest_chineseproblem.php?cid=658&pid=1003

题解：

f0(1)=2;  f0(2)=3;  f0(3)=4;

f1(1)=3;  f1(2)=4;  f1(3)=5;

f2(1)=4;  ......

所以归纳出：fn(x)=n+x+1;  orz

然后求euler(n+x+1).

代码：

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 using namespace std;
 typedef long long LL;

 LL euler_phi(LL x) {
     LL ret = x;
     for (LL i = ; i*i <= x; i++) {
         if (x%i == ) {
             ret = ret / i*(i - );
             while (x%i == ) x /= i;
         }
     }
     if (x > ) ret = ret / x*(x - );
     return ret;
 }

 int main() {
     LL n, x;
     while (scanf("%lld%lld", &n, &x) ==  && n) {
         printf("%lld\n", euler_phi(n + x + ));
     }
     return ;
 }