Cod sursa(job #2616712)
Utilizator | Denis Scutariu Yato2 | Data | 19 mai 2020 20:11:02 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.53 kb |
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n,phi[1000001];
long long s=0;
int main()
{
fin>>n;
for(int i=0; i<=n; i++)
phi[i]=i;
for(int i=2; i<=n; i++)
if(phi[i]==i)
{
phi[i]=i-1;
for(int j=2; j<=n/i; j++)
phi[j*i] = phi[j*i] / i * (i-1);
}
for(int i = 2; i <= n; i++)
s+=phi[i];
s=2*s+1;
fout<<s;
fin.close();
fout.close();
return 0;
}