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

typedef struct stack {
  int val;
  struct stack *next;
} stack;

stack *push(stack *st, int val) {
  stack *new = malloc(sizeof(stack));
  new->next = st;
  new->val = val;
  return new;
}

int isEmpty(stack *st) { return st == NULL; }

int peek(stack *st) { return st->val; }

stack *pop(stack *st) {
  stack *tmp = st->next;
  free(st);
  return tmp;
}

int main(void) {
  stack *st = NULL;

  int size = 0;
  int in;
  int last;
  int lastUsed = 0;
  int centFound = 0;

  while (scanf("%d,", &in) != EOF) {
    size++;
    if (!isEmpty(st) && peek(st) == in) {
      st = pop(st);
    } else if (lastUsed == 1 && last == in) {
      st = pop(st);
      st = pop(st);
      centFound = 1;
    } else {
      if (!isEmpty(st)) {
        last = peek(st);
        lastUsed = 1;
      }
      // printf("PUSHING: %d\n", in);
      st = push(st, in);
    }
  }

  if (size > 0 && isEmpty(st) && centFound == 1) {
    printf("Yes");
  } else if (size == 1) {
    printf("Yes");
  } else {
    printf("No");
  }

  return 0;
}