Cod sursa(job #2737231)
Utilizator | Matei Alexandru AlexGFX | Data | 4 aprilie 2021 15:57:02 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.55 kb |
#include <bits/stdc++.h>
using namespace std;
int N;
bool arr[2000002];
bool prim(int x) {
for(int i = 2; i <= sqrt(x); i++) {
if (x % i == 0) {
return false;
}
}
return true;
}
int main() {
freopen("ciur.in", "r", stdin);
freopen("ciur.out", "w", stdout);
cin >> N;
int ans = 0;
for(int i = 2; i <= N; i++) {
if(!arr[i]) {
if(prim(i)) {
ans++;
arr[i] = 1;
}
}
}
cout << ans;
}