#include<stdlib.h>

int strlen(const char* S)
{
	int k = -1;
	do
		k++;
	while (S[k] != '\0');
	return k;
}

int stradd(char** S, const char* add_str ) {
	int orig_len = strlen(*S);
	int add_len = strlen(add_str);
	int new_size = orig_len + add_len;
	char* new_str = (char*)malloc(sizeof(char) * (new_size + 1));
	if (new_str != NULL) {
		int k = 0;
		for (int i = 0; i < orig_len; i++)
			new_str[i] = S[i];
		for (int i = orig_len; i < new_size; i++, k++)
			new_str[i] = add_str[k];
		new_str[new_size] = '\0';
		*S = new_str;
	}
	else
		return -1;
}