#include<stdio.h>
#include<malloc.h>//内存分配头文件
#include<math.h>//在math.h中已定义OVERFLOW的值为3
#define SIZE 100
#define STACKINCREMENT 10
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
typedef int Status;
typedef struct   //栈的结构体
{
  char a;
} SElemType;
typedef struct
{
  SElemType *base;
  SElemType *top;
  int stacksize;
} SqStack;
typedef struct //QNode //队列的结构体
{
  char b;
  struct QNode * next;
} QNode,*QueuePtr;
typedef struct // 链队列类型
{
  QueuePtr front;  // 队头指针
  QueuePtr rear;  // 队尾指针
} LinkQueue;
//定义全局变量
SqStack S;
SElemType e;
LinkQueue Q;
QueuePtr p;
char f;
//栈操作
Status InitStack(SqStack *S)
{
  S->base=(SElemType *)malloc(SIZE*sizeof(SElemType));
  if(!S->base) exit(OVERFLOW);
  S->top=S->base;
  S->stacksize=SIZE;
  return OK;
}
Status Push(SqStack *S,SElemType e)
{
  if(S->top-S->base>=S->stacksize)
  {
    S->base=(SElemType *)malloc((S->stacksize+STACKINCREMENT)*sizeof(SElemType));
    if(!S->base) exit(OVERFLOW);
    S->top=S->base+S->stacksize;
    S->stacksize+=STACKINCREMENT;
  }
  *S->top++=e;
  return OK;
}
Status Stackempty(SqStack S)//栈是否为空
{
  if(S.top==S.base)
    return TRUE;
  else
    return FALSE;
}
Status Pop(SqStack *S,SElemType *e)
{
  if(S->top==S->base) return ERROR;
  *e=*--S->top;
  return OK;
}
Status StackLength(SqStack S)//求栈的长度
{
  return (S.top-S.base);
}
//队列操作
Status InitQueue(LinkQueue *Q)
{
  Q->front=(QueuePtr)malloc(sizeof(QNode));
  Q->rear=Q->front;
  if(!Q->front) exit(OVERFLOW);
  Q->front->next=NULL;
  return OK;
}
Status EnQueue(LinkQueue *Q,char f)
{
  p=(QueuePtr)malloc(sizeof(QNode));
  if(!p) exit(OVERFLOW);
  p->b=f;
  p->next=NULL;
  Q->rear->next=p;
  Q->rear=p;
  return OK;
}
Status DeQueue(LinkQueue *Q,char *f)
{
  if(Q->front==Q->rear) return ERROR;
  p=Q->front->next;
  *f=p->b;
  Q->front->next=p->next;
  if(Q->rear==p)
    Q->rear=Q->front;
  free(p);
  return OK;
}
Status QueueLength(LinkQueue Q)
{
  int i=0;
  p=Q.front;
  while(Q.rear!=p)
  {
    i++;
    p=p->next;
  }
  return i;
}
Status QueueEmpty(LinkQueue Q)
{
  if(Q.front==Q.rear)
    return TRUE;
  else
    return FALSE;
}
void main()
{
  int i,m;
  char n,a[20];
  InitStack(&S);
  InitQueue(&Q);
  gets(a);
  for(i=0; a[i]!='&'; i++) ///////////    &前的数据进栈
  {
    e.a=a[i];
    Push(&S,e);
  }
  for(i=i+1; a[i]!='\0'; i++) //////////   ‘ &'后的数据进入队列
    EnQueue(&Q,a[i]);
  if( StackLength(S)!=QueueLength(Q))    /////栈和队列的数据个数不一样
    printf("NO!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
  else
    while(!Stackempty(S)&&!QueueEmpty(Q))///////栈和队列里还有数据
    {
      Pop(&S,&e);
      m=e.a;
      DeQueue(&Q,&f);
      n=f;
      if(m!=n)
      {
        printf("NO!!!!!!!!!!!!!!!!!!!!!!");
        break;
      }
    }
  if(m==n&&Stackempty(S)&&QueueEmpty(Q))
    printf("YES!!!!!!!!!!!!!!!!!!!!!!");
}