Cod sursa(job #3204656)
Utilizator | Nemtisor Andrei andrei.n | Data | 17 februarie 2024 11:20:22 |
---|---|---|---|
Problema | Fractii | Scor | 0 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.63 kb |
#include <bits/stdc++.h>
using namespace std;
int phi[1000002];
void setPhi(int n)
{
for(int i=1 ; i<=n; i++)
phi[i] = i;
for(int i=2; i<=n; i++)
if(phi[i] == i)
{
phi[i]--;
for(int j=2; j * i<=n; j++)
phi[j * i] = phi[j * i] / i * (i - 1);
}
}
int main()
{
ifstream fin ("fractii.in");
ofstream fout ("fractii.out");
#define fin cin
#define fout cout
int n;
long long s=0;
fin>>n;
setPhi(n);
for(int i=1; i<=n; i++)
{
s += phi[i];
}
fout<<s*2-1;
return 0;
}