数制转换：a进制转换为b进制

#include<stdio.h>
#include<string.h>
int main()
{
	long int a, b;
	char num[100];
	while (scanf("%d%s%d", &a, num, &b) != EOF)
	{
		int length = strlen(num), c = 1; int temp=0;
		for (int i = length - 1; i >= 0; i--)
		{
			int x;
			if (num[i] >= '0'&&num[i] <= '9')
				x = num[i] - '0';
			else if (num[i] >= 'a'&&num[i] <= 'f')
				x = num[i] - 'a' + 10;
			else
				x = num[i] - 'A' + 10;
			temp += x * c;
			c *= a;
		}
		char buf[100]; int size = 0;
		do {
			int x = temp % b;
			if (x >= 10)
				buf[size++] = x - 10 + 'A';
			else
				buf[size++] = x + '0' ;
			temp = temp / b;
		} while (temp != 0);
		for (int i = size - 1; i >= 0; i--)
			printf("%c", buf[i]);
		printf("\n");
	}
	return 0;
}