Cod sursa(job #1400734)

Utilizator Iustin48Ventaniuc Iustin Iustin48 Data 25 martie 2015 13:39:20
Problema Fractii Scor 100
Compilator cpp Status done
Runda Arhiva de probleme Marime 0.35 kb
Raporteaza aceasta sursa 
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,a[1000001];
long long sol;
int main()
{
    f>>n;
    for(int i=2;i<=n;i++)
        a[i]=i-1;
    for(int i=2;i<=n;i++)
    {
        for(int j=i<<1;j<=n;j+=i)
            a[j]-=a[i];
        sol+=a[i];
    }
    g<<sol*2+1;
    return 0;
}