51Nod 1040 最大公约数之和

Posted 2020-11-03 jaydenouyang

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 
 5 using namespace std;
 6 typedef long long LL;
 7 
 8 LL Eular(LL m)
 9 {
10     LL res = m;
11     for(LL i=2; i*i<=m; i++)
12     {
13         if(m%i==0)
14         {
15             res -= res/i;
16             while(m%i==0)
17                 m /= i;
18         }
19     }
20     if(m > 1)
21         res -= res/m;
22     return res;
23 }
24 
25 int main()
26 {
27     LL m;
28     while(~scanf("%lld",&m))
29     {
30         LL ans = 0;
31         for(LL i=1; i*i<=m; i++)
32         {
33             if(m%i == 0){
34                 ans += Eular(m/i)*i;
35                 if(m != i*i)
36                     ans += m/i*Eular(i);
37             }
38         }
39         cout<<ans<<endl;
40     }
41     return 0;
42 }