Cod sursa(job #423864)
Utilizator | Data | 24 martie 2010 13:07:45 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.31 kb |
#include<cstdio>
int i,j,n,nr;
const int N = 1<<21;
bool ciur[N];
int main()
{
freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);
scanf("%d",&n);
for(i=2;i*i<=n;++i)
if(!ciur[i])
{
for(j=i*i;j<=n;j+=i)
ciur[j]=true;
}
for(i=2;i<=n;i++)
if(!ciur[i])
nr++;
printf("%d",nr);
return 0;
}