Cod sursa(job #2282978)
Utilizator | Data | 14 noiembrie 2018 19:59:36 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.61 kb |
#include <iostream>
#include <fstream>
using namespace std;
bool a[2000001];
int main()
{
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");
int n, x=0;
fin >> n;
for (int i=0; i<=n; i++)
{
a[i]=1;
}
a[0]=0;
a[1]=0;
for (int i=2; i<=n; ++i)
{
if (a[i]==0)
continue;
for ( int j=i+i; j<=n; j=j+i)
{
a[j]=0;
}
}
int k=0;
for ( int i=0; i<=n; i++)
{
if (a[i]==1)
{
k++;
}
}
fout <<k<<endl;
return 0;
}