Cod sursa(job #1362322)
Utilizator | Data | 26 februarie 2015 11:48:39 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.38 kb |
#include <fstream>
#include <math.h>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
long n,nr;
bool a[2000001];
int main()
{
long i,j;
f>>n;
for(i=2; i<=sqrt(n); ++i)
if(!a[i])for(j=2; i*j<=n; ++j)
a[i*j]=1;
for(i=n; i>=2; --i)
if(!a[i]) ++nr;
g<<nr;
f.close();
g.close();
return 0;
}