PNUMBER

Đề bài

Đáp án

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#include<iostream>
#include<math.h>
using namespace std;

int main(){
    bool arr[1000001];
    int a,b;
    cin>>a>>b;
    if(a<2) a=2;
    for(int i=1;i<=b;i++){
        arr[i] = true;
    }
    int sqr = sqrt(b);
    for(int i=2;i<=sqr;i++){
        if(arr[i]) {
            for(int j=i*i; j<=b;j+=i){
                arr[j] = false;
            }
        }
    }
    for(int i=a;i<=b;i++){
        if(arr[i]){
            cout<<i<<endl;
        }
    }
    return 0;
}