Cod sursa(job #3217689)
Utilizator | Rebegea Stefan ReBeGhEl | Data | 24 martie 2024 13:07:19 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.51 kb |
#include <fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
const int nMax=1e6;
int phi[nMax+5];
void make_phi(int n)
{
for(int i=2;i<=n;i++)
phi[i]=i;
for(int i=2;i<=n;i++)
{
if(phi[i]==i)
{
for(int j=i;j<=n;j+=i)
phi[j]=phi[j]/i *(i-1);
}
}
}
int main()
{
int n;
cin>>n;
make_phi(n);
int ans=0;
for(int i=2;i<=n;i++)
ans+=2*phi[i];
cout<<ans+1;
return 0;
}