Cod sursa(job #1124687)
Utilizator | Niculae Alexandru Vlad AlexNiuclae | Data | 26 februarie 2014 13:15:35 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.5 kb |
#include <cstdio>
using namespace std;
int n,cnt;
bool prim[2000005];
int ciur(int n)
{
int cnt=0;
for (int i=2;i<=n;i++)
prim[i]=true;
for (int i=2;i<=n;i++)
if (prim[i])
{
for (int j=i*2;j<=n;j+=i) prim[j]=false;
cnt++;
}
return cnt;
}
int main()
{
freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);
scanf("%d", &n);
cnt=ciur(n);
printf("%d", cnt);
return 0;
}