Pagini recente » Borderou de evaluare (job #1400739) | Borderou de evaluare (job #2580775) | Monitorul de evaluare | Cod sursa (job #1678938) | Cod sursa (job #895594)
Cod sursa(job #895594)
#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=2;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;
}