#include<iostream>
#include<cstring>
using namespace std;

void copy_string(char *destination, char *source){  // strcpy
	while(*destination++ = *source++);
}

void append_string(char *destination, char *source){ // strcat
	while(*destination++);
	destination -= 1;
	while(*destination++ = *source++);
}

size_t  string_length(char *string){ // strlen
	size_t len = 0;
	while(string[len])
		len++;
	return len;
}

int main(){
	char a1[] = "Sheep";
	char a2[] = "Goat";
	char a3[20];

	copy_string(a3, a1);
	append_string(a3, a2);

	cout << "a3 = " << a3 << endl;
	cout << "a1 length " << string_length(a1) << endl;
	return 0;
}