int isGood(const char *filename) {
	FILE *f = fopen(filename, "r");

	if( !f )
		return 0;

	int c;

	while( (c = fgetc(f)) != EOF ) {
		if( c == '\n' || c == '\r' )
			continue;

		if( c <= '0' || c >= '9' )
			return 0;
	}

	fclose(f);

	return 1;
}