#include <vector> 
#include <iostream>
#include <cassert>

template<size_t ROWS, size_t COLS>
size_t convertIndex(size_t row, size_t col)
{
	assert(row < ROWS && col < COLS);
	return row * COLS + col;
}

int main() 
{
	std::vector<int> v =
	{
		0,1,2,3,4,
		5,6,7,8,9
	};

	std::cout << v[convertIndex<2, 5>(1, 3)];
}