Cod sursa(job #273380)
Utilizator | Data | 8 martie 2009 15:11:00 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 20 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.3 kb |
#include<fstream.h>
int ok[10000];
int n,i,j,k;
int main()
{
ifstream f("ciur.in");
ofstream g("ciur.out");
f>>n;
k=1;
for(i=3;i*i<=n;i+=2)
if(ok[i]==0)
for(j=2*i;j<=n;j+=i)
ok[j]=1;
for(i=3;i<=n;i+=2)
if(ok[i]==0)k++;
g<<k<<'\n';
f.close();
g.close();
return 0;
}