Cod sursa(job #2486157)
Utilizator | Buzatu Giulian Giulian617 | Data | 2 noiembrie 2019 13:14:01 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.51 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
char pr[2000005];
void Ciur()
{
pr[0]=pr[1]=1;
for(int i=4; i<=2000000; i+=2)
pr[i]=1;
for(int i=3; i*i<=2000000; i+=2)
if(pr[i]==0)
{
for(int j=i*i; j<=2000000; j+=i)
pr[j]=1;
}
}
int main()
{
int n,cnt=0;
f>>n;
Ciur();
for(int i=2; i<=n; i++)
if(pr[i]==0)
cnt++;
g<<cnt;
return 0;
}