View Code of Problem 101

#include<stdio.h>
#include<string.h>
int main(){
	int n,i;
	char a[1000],b[1000];
	while(scanf("%s",&a)!=EOF){
		int len=strlen(a);
		int count=1;
		for(i=len-1;i>=0;i--){
			if(a[i]>='0'&&a[i]<='9'){
				if(count%4==0)
					b[count++]=',';
				b[count++]=a[i];
			}
		}
		for(i=count-1;i>=1;i--)
			printf("%c",b[i]);
		printf("\n");
	}
}