#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

/* rearrange things so instead of
   0 1
   0 2
   0 3
   1 4
   1 5
   1 6
   we just print
   0   1 2 3 
   1   4 5 6
*/

int main(void)
{
	uint32_t dac, adc;
	uint32_t olddac;
	int first = 1;
	
	while(1) {
		scanf("%d %d", &dac, &adc);
		if (feof(stdin))
			break;
		if (first) {
			printf("%ld   ", dac);
			first = 0;
		} else if (dac != olddac) {
			printf("\n%ld   ", dac);
		} else {
			printf(" ");
		}
		printf("%ld", adc);
		olddac = dac;
	}
	printf("\n");
	return 0;
}