Cod sursa(job #2783644)
Utilizator | Data | 14 octombrie 2021 20:28:21 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 0 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.54 kb |
#include <fstream>
using namespace std;
int ciur[2000001];
int main()
{
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n;
fin >> n;
ciur[0] = 1;
ciur[1] = 1;
for (int d = 2; d * d <= 2000000; d++)
{
if (!ciur[d])
{
for (int i = d * d; i <= 2000000; i += d)
{
ciur[i] = 1;
}
}
}
int ans = 0;
for (int i = 2; i <= n; i++)
{
ans += !ciur[i];
}
fout << ans;
return 0;
}