View Code of Problem 101

#include<stdio.h>
#include<string.h>
void main()
{
	char a[1000];
	char b[1000];
	while (scanf("%s",a)!=EOF)
	{
		int len = strlen(a);
		int c = 0, t = 1;
		for (int i = len-1; i >= 0; i--)
		{
			if (a[i] == ',') continue;
			else
			{
				b[c++] = a[i] ;
			}
			if ((t++) % 3 == 0 && i != 0)
			{
				b[c++] = ',';
			}
		}
		for (int i = c-1; i >=0; i--)
		{
			printf("%c", b[i]);
		}
		printf("\n");
	}
}