#include <stdio.h>

int	getnum(int	base)
{
	char	buf[256];
	int	ch, index, value, newdigit;

	if (fgets(buf,sizeof buf,stdin)) {
		value = 0;
		for (index = 0; (ch = buf[index]) != '\n' && ch != '\0'; ++index) {
			if (ch >= '0' && ch <= '9') {
				newdigit = ch - '0';
			} else if (ch >= 'A' && ch <= 'Z') {
				newdigit = ch - 'A' + 10;
			} else if (ch >= 'a' && ch <= 'z') {
				newdigit = ch - 'a' + 10;
			} else {
				printf("Illegal character for base %d (%c)\n",base,ch);
				return -1;
			}
			if (newdigit >= base) {
				printf("Illegal digit for base %d (%c)\n",base,ch);
				return -1;
			}
			value *= base;
			value += newdigit;
		}
		return value;
	} else	return -1;
}
void	putnum(int	value,
	       int	base)
{
	int	quotient, remainder;

	remainder = value % base;
	quotient = value / base;
	if (quotient > 0) putnum(quotient,base);
	if (remainder < 10) putchar('0' + remainder);
	else putchar('A' + remainder - 10);
}
int	main(void)
{
	int	base, value;

	for (;;) {
		fputs("input base: ",stdout);
		base = getnum(10);
		if (base <= 1) return 0;
		fputs("value: ",stdout);
		value = getnum(base);
		if (value < 0) return 0;
		fputs("value in base 10: ",stdout);
		putnum(value,10); putchar('\n');
		fputs("output base: ",stdout);
		base = getnum(10);
		if (base <= 1) return 0;
		fputs("value in that base: ",stdout);
		putnum(value,base); putchar('\n');
	}
}