Cod sursa(job #2632749)

Utilizator etohirseCristi Cretu etohirse Data 4 iulie 2020 18:22:01
Problema Fractii Scor 100
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 0.31 kb
Raporteaza aceasta sursa 
#include <bits/stdc++.h>
using namespace std;

const int mxN=1e6+5;
long long n, ans, v[mxN];

int main(){
	ifstream cin("fractii.in");
	ofstream cout("fractii.out");
	cin >> n;
	for(int i=2; i<=n; ++i)
		v[i]=i-1;
	for(int i=2; i<=n; ++i){
		ans+=v[i];
		for(int j=i*2; j<=n; j+=i)
			v[j]-=v[i];
	}
	cout << 2*ans+1;
}