func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long N = 2e5 + 10, M = N, INF = 0x3f3f3f3f, mod = 1e9 + 7,                   base = 131;   long long n, t, ans;   long long a[N], s[N];   long long phi(long long n) {     long long res, a;     res = a = n;     for (long long i = 2; i <= a / i; i++) {       if (a % i) continue;       res = res / i * (i - 1);       while (a % i == 0) a /= i;     }     if (a > 1) res = res / a * (a - 1);     return res;   }   signed main() {     long long p;     cin >> p;     cout << phi(p - 1);     return 0;   }   