View Code of Problem 101

#include "stdio.h"
#include "stdlib.h"
#include "ctype.h"
#include "string.h"
#define Max 100
int main()
{
	char a[100],b[100];
	int i;
	while(gets(a)!=NULL)
	{
		int cnt=0,j=0;
		for(i=strlen(a)-1;i>=0;i--)
		{
			if(isdigit(a[i]))
			{
				if(cnt==3)
				{
					b[j++]=',';
					cnt=0;
				}
				b[j++]=a[i];
				cnt++;
			}
		}
		j--;
		for(i=j;j>=0;i--)
			printf("%c",b[i]);

		printf("\n");
	}

	return 0;
}