Cod sursa(job #348584)
Utilizator | Data | 16 septembrie 2009 10:16:49 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.33 kb |
#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
bool v[2000000];
int main()
{
int n,nr,i,j;
in>>n;
for(i=2;i*i<=n;i++){
if(v[i]==0){
for(j=i*i;j<=n;j+=i){
v[j]=1;
}
}
}
nr=0;
for(i=2;i<=n;i++){
nr=nr+(1-v[i]);
}
out<<nr<<"\n";
return 0;
}