#include <stdio.h>
#include <string.h>

char s[50000][25];
int len[50000], idx;

int main() {
	int test;
	scanf("%d", &test);
	while(test--) {
		char op[3];
		scanf("%s", op);
		if (op[0] == 'I') {
			char str[25];
			scanf("%s", str);
			for (int i = idx - 1; i >= 0; i--) {
				for (int j = 0; j < len[i]; j++)
					s[i + 1][j] = s[i][j];
				len[i + 1] = len[i];
			}
			len[0] = strlen(str);
			for (int i = 0; i < len[0]; i++)
				s[0][i] = str[i];
			idx++;
		} else if (op[0] == 'R') {
			for (int i = 0; i < idx; i++) {
				for (int j = 0; j < len[i]; j++)
					s[idx * 2 - i - 1][j] = s[i][j];
				len[idx * 2 - i - 1] = len[i];
			}
			idx *= 2;
		} else if (op[0] == 'D') {
			for (int i = 0; i < idx; i++) {
				for (int j = 0; j < len[i]; j++)
					s[i + idx][j] = s[i][j];
				len[i + idx] = len[i];
			}
			idx *= 2;
		} else if (op[0] == 'S') {
			if (idx == 0)
				printf("NULL");
			for (int i = 0; i < idx; i++) {
				for (int j = 0; j < len[i]; j++)
					printf("%c", s[i][j]);
				printf(" ");
			}
			printf("\n");
		}
	}
	return 0;
}