Cod sursa(job #1736593)
Utilizator | Data | 2 august 2016 10:44:39 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.48 kb |
#include <fstream>
using namespace std;
int n,v[1000005],i,j;
unsigned long long s;
int main()
{
ifstream f("fractii.in");
ofstream g("fractii.out");
f>>n;
s=1;
for(i=2; i<=n; i++)
v[i]=i;
for (i=2; i<=n; i++)
{
if (v[i]==i)
{
for (j=i; j<=n; j+=i)
v[j]=v[j]/i*(i-1);
}
}
for (i=2; i<=n; i++)
s+=2*v[i];
g<<s<<'\n';
f.close(); g.close();
return 0;
}