Cod sursa(job #1876557)
Utilizator | Buda Adrian adrian.buda | Data | 12 februarie 2017 14:24:41 |
---|---|---|---|
Problema | Fractii | Scor | 0 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.44 kb |
#include <fstream>
#include <cmath>
#define N 1000000
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int phi[1000000];
int main()
{
int i,j,n,s;
in>>n;
for (int i=1;i<=N;i++) phi[i]=i;
for (int i=2;i<=n;i++)
if (phi[i]==i)
for (j=i;j<=n;j+=i) phi[j] /=i, phi[j] *= (i-1);
s=1;
for(i=2;i<=n;i++)
{
s=s+2*phi[i];
}
out<<s;
return 0;
}