BZOJ2705: [SDOI2012]Longge的问题

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstdlib>
 4 #include <cstring>
 5 #include <cmath> 
 6 #define min(a, b) ((a) < (b) ? (a) : (b))
 7 #define max(a, b) ((a) > (b) ? (a) : (b))
 8 
 9 long long n;
10 
11 long long phi(long long x)
12 {
13     long long ans = x;
14     long long ma = sqrt(x);
15     for(register long long i = 2;i <= ma;++ i)
16         if(x % i == 0)
17         {
18             ans -= ans/i;
19             while(x % i == 0)x /= i;
20         }
21     if(x > 1)ans -= ans/x;//显然>根号n的n的质因数只有一个
22     return ans;
23 }
24 int main()
25 {
26     scanf("%d", &n);
27     register long long last, ans = 0;
28     register long long ma = sqrt(n);
29     for(register long long d = 1;d <= ma;++ d)
30     {
31         if(n % d == 0)
32         {
33             ans += phi(d) * (n/d);
34             if(d * d != n)ans += phi(n/d) * (d);
35         }
36     }
37     printf("%lld", ans);
38     return 0;
39 }