#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	for(int i=2;i<=sqrt(n);i++){
		if(n%i==0){
			cout<<"no";
			return 0;
		}
	}
	cout<<"yes";
	return 0;
}

C++ :

#include<bits/stdc++.h>
using namespace std;
int ss(int x){
	if(x<2)return false;
	if(x==2)return true;
	for(int i=2;i<=sqrt(x)+1;i++){
		if(x%i==0)return false;
	}
	return true;
}

int main(){
	int a;
	cin>>a;
	if(ss(a))cout<<"yes";
	else cout<<"no";
	return 0;
}

Python :

# coding=utf-8
n=int(input())
flag=0
for i in range(2,n):
    if n%i==0:
        flag=1
        print("no")
        break
if flag==0:
    print("yes")