C :

#include<stdio.h>
#include<math.h>
int prime(int n)
{
	for(int i = 2; i * i <= n; i++)
		if(n % i == 0)
			return 0;
		return 1;
}
int main()
{
	int a;
	scanf("%d", &a);
	if(prime(a))
		puts("prime");
	else
		puts("not prime");
}

C++ :

#include<iostream>
using namespace std;
void judge(int a)
{
    int b=2;
    while(b<a&&a%b)
        b++;
    if(b==a)
        cout<<"prime"<<endl;
    else cout<<"not prime"<<endl;
}
int main()
{
    int a;
    cin>>a;
    judge(a);
}