Cod sursa(job #557641)

Utilizator Claudiu95Vartolomei Alexandru Claudiu Claudiu95 Data 16 martie 2011 19:02:26
Problema Fractii Scor 100
Compilator cpp Status done
Runda Arhiva de probleme Marime 0.32 kb
Raporteaza aceasta sursa 
#include<fstream>
using namespace std;
long long unsigned int phi[1000005],i,j,N,s=1;
ifstream fin("fractii.in");ofstream fout("fractii.out");
int main(){
	fin>>N;
	for(i=1;i<=N;++i)
		phi[i]=i-1;
	for(i=2;i<=N;++i)
		for(j=2*i;j<=N;j+=i)
			phi[j]-=phi[i];
	for(i=2;i<=N;i++)
		s+=2*phi[i];
	fout<<s;
	return 0;
}