Cod sursa(job #2690701)
Utilizator | Data | 25 decembrie 2020 13:08:30 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.48 kb |
#include <fstream>
using namespace std;
bool ciur[2000005];
int main()
{
ifstream fin("ciur.in");
ofstream fout("ciur.out");
ciur[0]=ciur[1]=1;
for(int i=2;i*i<=2000000;i++)
{
if(ciur[i]==0)
{
for(int j=i*i;j<=2000000;j+=i)
{
ciur[j]=1;
}
}
}
int n,cnt=0;
fin>>n;
for(int i=1;i<=n;i++)
{
if(ciur[i]==0)
{
cnt++;
}
}
fout<<cnt<<'\n';
return 0;
}