/*
Author: NgThi Thao Duyen
Link submit:
*/
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define task "LEAD"
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
#define dou double
#define el '\n'
#define ull unsigned long long
#define pll pair<ll,ll>
const ll maxN = 1e6;
const ll maxM = 1e3;
const ll LIM = 1e9;
const ll oo = 1e18;
const ll mod = (ll)1e9+7;
const ll LOG = 23;
int num;
int check_prime(int num)
{
if(num < 2) return 0; //không là số nguyên tố => trả về 0
//Ngược lại thì kiểm tra từ 2 -> sqrt(num)
for(int i=2; i*i<=num; i++)
{
if(num % i == 0) return 0;
//nếu num chia hết cho một số i (khác bằng num)
//=>vi phạm điều kiện chỉ chia hết cho 1 và chính nó => trả về 0
}
//Nếu đã kiểm tra một lượt mà thoả mãn thì return về 1
return 1;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
if(fopen(task".inp","r"))
{
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin >> num;
if(check_prime(num)) cout<<"YES";
else cout<<"NO";
return 0;
}
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