Cod sursa(job #652437)
Utilizator | Data | 24 decembrie 2011 14:38:57 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.45 kb |
#include<iostream>
#include<fstream>
#include<cmath>
using namespace std;
long n,i,j,s;
bool V[20000000];
ifstream in("ciur.in");
ofstream out("ciur.out");
int main()
{
in>>n;
for ( i=2; i<=sqrt(n); i++)
if ( V[i]==0 )
{
for ( j=i*i; j<=n; j+=i )
V[j]=1;
}
for ( i=2; i<=n; ++i )
{
if ( V[i]==0 )
s++;
}
out<<s<<"\n";
return 0;
}