Cod sursa(job #2251111)
Utilizator | Macovei Rares-Stefan RaresMacovei | Data | 1 octombrie 2018 09:50:27 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.44 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bool ciur[2000001];
void Ciur(int n){
int i,j;
ciur[0]=1,ciur[1]=1;
for(i=4;i<=n;i+=2) ciur[i]=1;
for(i=3;i*i<=n;i+=2)
for(j=i*i;j<=n;j+=2*i) ciur[j]=1;
}
int main()
{
int n,i,k=0;
fin>>n;
Ciur(n);
for(i=2;i<=n;++i){
if(ciur[i]==0)k++;
}
fout<<k;
return 0;
}