Cod sursa(job #652435)
Utilizator | Data | 24 decembrie 2011 14:33:52 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.38 kb |
#include<iostream>
#include<fstream>
using namespace std;
long n,i,j,s;
bool V[20000000];
ifstream in("ciur.in");
ofstream out("ciur.out");
int main()
{
in>>n;
s=1;
for ( i=3; i<=n; i+=2 )
if ( V[i]==0 )
{
s++;
for ( j=i*i; j<=n; j+=i )
V[j]=1;
}
out<<s<<"\n";
return 0;
}