Cod sursa(job #1693648)
Utilizator | Data | 23 aprilie 2016 16:58:49 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.53 kb |
#include <iostream>
#include <fstream>
using namespace std;
int np[1000005];
void euler(int n) {
for(int i=1;i<=n;i++)
np[i]=i;
for(int i=2;i<=n;i++)
if(np[i]==i) {
for(int j=i;j<=n;j+=i)
np[j]/=i,np[j]*=(i-1);
}
}
int main()
{
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n;
fin>>n;
euler(n);
long long int fractii=0;
for(int i=1;i<=n;i++)
fractii+=2*np[i];
fout<<fractii-1;
return 0;
}