// This program prints a list of prime numbers from
// 1 to 100.

#include <iostream>
#include <math.h>
bool isprime(int);
int nth_prime(int n);

int main()
{
	int n;

	cout << "Enter n: ";
	cin >> n;
	cout << "The nth prime number is " << nth_prime(n) << endl;

}

// john's function:
// this function determines the n'th prime number
// the 1st prime number is 1
//     2nd prime number is 2
//     3rd prime number is 3
//     4th prime number is 5
//     5th prime number is 7
//     6th prime number is 11
// 'n' is the index of the prime number we want to compute
// the first column of numbers in the table corresponds to 'counter'
// the second column of numbers in the table corresponds to 'i'

int nth_prime(int n)
{
	int i;
	int counter = 0;

	for (i=1; counter < n ; i++) 
	{
		if (isprime(i))
		{
            counter = counter + 1;
		}
	}
	// must decrement i by 1 because for loop added 1 to i before exiting
	return i-1;
}

bool isprime(int p)
{
	int i;
	int stopval;
	bool pisprime;

	stopval = int(sqrt(p) + .5);

	// DECIDE IF IT IS A PRIME
	pisprime = true;

	for (i=2; i<=stopval && pisprime; ++i)
	{
		// can p be divided by i with no remainder
		if (p % i == 0)
			pisprime = false;
	}

	return pisprime;
}