Cod sursa(job #2590436)
Utilizator | Mariciuc Andrei-Alexandru Andrei1 | Data | 27 martie 2020 22:11:46 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.62 kb |
#include <bits/stdc++.h>
using namespace std;
//phi cate numere de la 1 la n sunt coprime cu n!
int main()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
int n;
cin>>n;
vector<int> phi(n+1);
for(int i=0; i<=n; i++)
phi[i]=i;
for(int i=2; i<=n; i++)
{
if( phi[i] == i )//este prim
{
for(int j=i; j<=n; j+=i)
{
phi[j]/=i;
phi[j]*=(i-1);
}
}
}
int suma=0;
for(int i=1; i<=n; i++)
suma+=2*phi[i];
cout<<suma-1;
return 0;
}