Cod sursa(job #447768)
| Utilizator |  FMI Romila Remus Arthur R.A.R |
Data | 30 aprilie 2010 22:40:24 |
|---|---|---|---|
| Problema | Fractii | Scor | 50 |
| Compilator | cpp | Status | done |
| Runda | Arhiva de probleme | Marime | 0.33 kb |
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int main ()
{
long long val = 0;
int n,i,j,phi[100000];
in>>n;
for(i=1;i<=n;i++)
phi[i] = i-1;
for(i=2;i<=n;i++)
for(j=2*i;j<=n;j+=i)
phi[j]-=phi[i];
for(i=2;i<=n;i++)
val+=phi[i];
out<<(2*val)+1;
return 0;
}