class CQueue {
public:
stack<int> stack1;
stack<int> stack2;
CQueue() {}

void appendTail(int value) {
stack1.push(value);
}

int deleteHead() {
if (stack1.empty()) return -1;

while (!stack1.empty()){ // 1 -> 2
int tmp = stack1.top();
stack1.pop();
stack2.push(tmp);
}
// delete head
int res = stack2.top();
stack2.pop();
while (!stack2.empty()){ // 1 <- 2
int temp = stack2.top();
stack2.pop();
stack1.push(temp);
}
return res;
}
};