Cod sursa(job #1724097)
Utilizator | Data | 2 iulie 2016 12:40:25 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.49 kb |
#include <fstream>
using namespace std;
int a[1000005],n;
void Phi(int n)
{
int i,j;
for(i=2;i<=n;i++)
a[i]=i-1;
for(i=2;i<=n;i++)
for(j=i+i;j<=n;j=j+i)
a[j] = a[j] - a[i];
}
int main()
{
int i;long long S;
Phi(1000000);
ifstream fin("fractii.in");
ofstream fout("fractii.out");
fin>>n;
S=1;
for(i=2;i<=n;i++)
S=S+2*a[i];
fout<<S<<"\n";
fin.close();
fout.close();
return 0;
}