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  1. #include <bits/stdc++.h>
  2.  
  3. #define ll long long
  4. #define el cout << '\n'
  5.  
  6. using namespace std;
  7.  
  8. ll n, ans;
  9.  
  10. int main()
  11. {
  12.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  13.     if (fopen("MATH_IS_FUN.INP", "r"))
  14.     {
  15.         freopen("MATH_IS_FUN.INP", "r", stdin);
  16.         freopen("MATH_IS_FUN.OUT", "w", stdout);
  17.     }
  18.     cin >> n;
  19.     ans = n > 1 ? n : 0;
  20.     for (ll i = 2; i * i <= n; i++)
  21.     {
  22.         bool flag = 0;
  23.         while (n % i == 0)
  24.         {
  25.             n /= i;
  26.             flag = 1;
  27.         }
  28.         if (flag) ans -= ans/i;
  29.     }
  30.     if (n > 1) ans -= ans/n;
  31.     cout << ans;
  32. }
Success #stdin #stdout 0.01s 5308KB
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https://ideone.com/vu0xdf
language:
C++14 (gcc 8.3)
created:
5 hours ago
visibility:
public

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