Write a function that finds the number of solutions of the system in natural numbers (ℕ∪{0}):
x_1+x_2+x_3+x_4+x_5=100; x_1<10; 10≤x_2<30; x_4>20; x_5<30.

#include <iostream>
#include <cmath>
int main()
{
	size_t n;
	std::cin >> n;
	size_t count(0);

	for (size_t i = 0; i < 10; i++)
		for (size_t j = 10; j < 30; j++)
			for (size_t k = 10; k < 30; k++)
				for (size_t l = 21; l < n; l++)
					for (size_t m = 0; m < 30; m++)
						if (i + j + k + l + m == n)
							count++;
	std::cout << count << std::endl;
	return 0;
}