栈操作的正确性

Time Limit:1000 ms | Memory 对输入序列执行一组栈操作，判断操作是否正确。

Input

每行是一个测试用例，表示一个操作序列。操作序列由P和Q两个符号组成，P表示入栈，Q表示出栈。操作序列长度不超过1000。

Output

对每个操作序列，若操作序列正确，即操作结束时栈中刚好为空，则输出Y；

若操作序列有错误，如栈空时执行出栈操作，或操作结束时栈中不空，则输出N。

-The correctness of the stack operation Time Limit: 1000 ms | Memory of the implementation of a set of input sequences stack operation, determine whether the operation is correct. Input Each line is a test case that an action sequence. Operation sequence from the P and Q are two symbols, P said stack, Q expressed stack. Operation sequence length not exceeding 1000. Output for each action sequence, if the correct sequence of operation, that operation is just the end of the stack is empty, the output Y　if the operation sequence of errors, such as the implementation of the stack when the stack space operation, or operation at the end of the stack is not empty, the output N.