Cod sursa(job #1322898)
Utilizator | Daniel Constantin Anghel Magnvs | Data | 20 ianuarie 2015 15:05:25 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.48 kb |
#include <bitset>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
const int nmax = 2000000;
bitset <nmax+1> sift;
int main( ) {
int n;
fin >> n;
int sol = 0;
for ( int i = 2; i <= n; ++ i ) {
if ( sift[i] == 0 ) {
++ sol;
for ( int j = 2*i; j <= n; j += i ) {
sift[j] = 1;
}
}
}
fout << sol << "\n";
return 0;
}