Cod sursa(job #570432)
Utilizator | Bruda Claudiu-Marcel claudiu725 | Data | 3 aprilie 2011 01:58:45 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.39 kb |
#include<fstream>
#include<cmath>
using namespace std;
const int N = 1000001;
int d[N];
int main()
{
int n,i,j;
long long s=0;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
fin>>n;
for (i=2;i<=n;i++)
d[i]=i-1;
for (i=2;i<=n;i++)
{
for (j=2*i;j<=n;j+=i)
d[j]-=d[i];
s+=d[i];
}
fout<<2*s+1<<'\n';
fin.close();
fout.close();
return 0;
}