#include <iostream>
#include <string.h>

using namespace std;

template<size_t N>
constexpr size_t strlen_(const char (&data)[N]) noexcept{
    return N - 1;
}

int main()
{
	const char hello_world[] = {'a','b','\0','e','f'};
	cout << strlen_(hello_world) << endl; // Wrong. Even if the zero was not there.
	cout << strlen(hello_world) << endl;
	
	// your code goes here
	return 0;
}