Cod sursa(job #2742589)
Utilizator | Data | 21 aprilie 2021 11:11:13 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.42 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int phi[1000005];
int main()
{
int n;
fin>>n;
int i,j;
for(i=1; i<=n; i++)
phi[i]=i;
for(i=1; i<=n/2; i++)
for(j=2*i; j<=n; j+=i)
phi[j]-=phi[i];
long long sum=0;
for(i=1; i<=n; i++)
sum+=phi[i];
fout<<sum*2-1<<"\n";
return 0;
}