Cod sursa(job #1975643)
Utilizator | Data | 1 mai 2017 16:23:28 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.41 kb |
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,phi[1000001];
long long nr=1;
void make_phi()
{
for(int i=1;i<=n;i++)
phi[i]=i-1;
for(int i=2;i<=n;i++)
for(int j=2*i;j<=n;j+=i)
phi[j]-=phi[i];
}
int main()
{
f>>n;
make_phi();
for(int i=2;i<=n;i++)
nr+=2*phi[i];
g<<nr;
return 0;
}