#include <queue>
#include <iostream>
 
int main() {
    std::queue<char> q;
    q.push('a');
    q.emplace('b');
    q.push('c');
    q.pop();
    std::cout << q.front() << std::endl;
    std::cout << q.back() << std::endl;
    std::cout << q.size() << std::endl;
}