Cod sursa(job #632887)

Utilizator OpportunityVlad Negura Opportunity Data 12 noiembrie 2011 15:00:29
Problema Fractii Scor 90
Compilator cpp Status done
Runda Arhiva de probleme Marime 0.33 kb
Raporteaza aceasta sursa 
#include<fstream>
using namespace std;
long long a[1000100],i,j,n,s=1;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main(){

  fin >> n;

  for (i=1; i<=n; i++)
   a[i]=i-1;
  for (i=2; i<=n; i++)
   for (j=i*2; j<=n; j+=i)
    a[j]-=a[i];
  for (i=1; i<=n; i++)
   s+=a[i]*2;

  fout << s;

 return 0;
}