#ifndef ZIPCODE_H
#define ZIPCODE_H
#include <iostream> //for class ostream
#include <string>   //for class string
using namespace std;

template <int N>
class zipcode {
private:
	string digits;
public:
	zipcode(const string& s) {
		if (s.size() != N) {
			cerr << "zipcode<" << N << "> must have N chars, not " << s.size() << ".\n";
			exit(EXIT_FAILURE);
		}

		if (s.find_first_not_of("0123456789") != string::npos) { //if we found a non-digit
			cerr << "zipcode<" << N << "> must have only digits.\n";
			exit(EXIT_FAILURE);
		}

		digits = s;
	}

	friend ostream& operator<<(ostream& ost, const zipcode<N>& zip) {
		return ost << zip.digits;
	}
};
#endif