#include <stdio.h>
#include <stddef.h>

int main(int argc, char **argv)
{
	char a='a';
	char b='a';
	char c='a';
	FILE *fp=fopen("letters.txt","w");
	
	while (1)
	{
		fprintf(fp,"%c%c%c\n",a,b,c);
		
		if (c++=='z')
		{
			c='a';
			
			if (b++=='z')
			{
				b='a';
				if (a++=='z')
				{
					// this was "zzz"
					break;
				}
			}
		}
	}
	
	fclose(fp);
}