#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 1000
#define MAX_STR 18

typedef struct {
    int tamanho;
    int paginas[MAX];
    struct STACK *stack;
} STACK;

void push(STACK *stack, int valor) {
    stack->paginas[stack->tamanho++] = valor;
}

int pop(STACK *stack) {
    return stack->paginas[--stack->tamanho];
}

STACK* criarStack() {
    STACK *pilha = (STACK*)malloc(sizeof(STACK));
    pilha->tamanho = 0;
    return pilha;
}

void clear_f(STACK *forward){
  while(forward->tamanho > 0){
    pop(forward);
  }
}

int main() {
  char stri[MAX_STR];

  STACK *stack = criarStack();
  STACK *back = criarStack();
  STACK *forward = criarStack();

  while(scanf("%s", stri) != EOF){
    if(strcmp(stri, "ENTER")==0) {
      push(back, 1);
      clear_f(forward);
    }
    else if(strcmp(stri, "BACK")==0) {
      pop(back);
      push(forward, 1);
    }
    else if(strcmp(stri, "FORWARD")==0) {
      pop(forward);
      push(back, 1);
    }
  }

  back->tamanho = back->tamanho-1;

  printf("BACK: %d\nFORWARD: %d", back->tamanho, forward->tamanho);
}