Cod sursa(job #3186330)
Utilizator | Balan Alexandru-Cristian Alex__balan | Data | 22 decembrie 2023 18:38:40 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.6 kb |
#include <bits/stdc++.h>
#include <fstream>
using namespace std;
const int N=1000007;
int e[N];
ifstream fin ("fractii.in");
ofstream fout ("fractii.out");
int main()
{
int n;
long long s=0;
fin>>n;
for (int i=2 ; i<=N ; i++)
{
e[i]=i;
}
e[1]=1;
for (int i=2 ; i<=N ; i++)
{
if (e[i]==i)
{
for (int mult=i; mult<=N ; mult+=i)
{
e[mult]=e[mult]/i*(i-1);
}
}
}
for (int i=1 ; i<=n ; i++)
{
s+=2*e[i];
}
s--;
fout<<s;
}