Cod sursa(job #895613)
Utilizator | Domnita Dan tandura | Data | 27 februarie 2013 11:59:39 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.55 kb |
#include <iostream>
#include <fstream>
using namespace std;
int phi[1000001];
int main()
{
int i,n,j,sum;
ifstream f("fractii.in");
f>>n;
for (int i=2;i<=n;i++)
phi[i]=i;
for (i=2;i<=n;i++)
if (phi[i]==i)
for (j=i+i;j<=n;j+=i)
phi[j]=phi[j]*(i-1)/i;
for(i=1;i<=n;i++)
if(phi[i]==i)
phi[i]--;
sum=0;
for(i=2;i<=n;i++)
sum+=phi[i];
ofstream g("fractii.out");
g<<(2*sum)+1<<"\n";
f.close();
g.close();
return 0;
}