1 //2017-08-04
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 #include <algorithm>
 6 
 7 using namespace std;
 8 
 9 int phi(int n){
10     int ans = n;
11     for(int i = 2; i*i <= n; i++){
12         if(n%i==0){
13             ans -= ans/i;
14             while(n%i==0)
15                 n /= i;
16         }
17     }
18     if(n > 1)ans = ans - ans/n;
19     return ans;
20 }
21 
22 int main()
23 {
24     int num;
25     while(scanf("%d", &num)!=EOF){
26         printf("%d\n", phi(num-1));
27     }
28 
29     return 0;
30 }