Cod sursa(job #370420)
Utilizator | Data | 1 decembrie 2009 11:25:52 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.43 kb |
#include<fstream>
#include<cstdlib>
#define MAXN 2000010
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
long n,i,j,nr;
char v[MAXN];
int main ()
{
f>>n;
v[0]=1;
v[1]=1;
i=3;
nr=1;
while(i<=n)
{
while(v[i]==1&&i<=n)
i+=2;
if(i<=n)
nr++;
j=i*i;
while(j<=n)
{
v[j]=1;
j+=i;
}
i+=2;
}
g<<nr<<'\n';
f.close();
g.close();
return 0;
}