Cod sursa(job #489015)

Utilizator ladybalexandra dinculescu ladyb Data 30 septembrie 2010 18:55:09
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.34 kb
Raporteaza aceasta sursa 
#include<cstdio>

const int N=2000002;

bool c[N];

int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int n;
	scanf("%d",&n);
	for (int i=2;i*i<=n;++i)
		if (!c[i])
			for (int j=i*i;j<=n;j+=i)
				c[j]=true;
	int nr=0;
	for (int i=2;i<=n;++i)
		if (!c[i])
			++nr;
	printf("%d\n",nr);
	return 0;
}