为啥全是MLE

#include <bits/stdc++.h>
using namespace std;

int m;
long long a,x;
string c;

deque<int> q[1000000];

int main(){
	cin >> m;
	for(int i=0;i<m;i++){
		cin >> c;
		cin >> a;
		if(c == "push_back"){
			cin >> x;
			q[a].push_back(x);
		}
		if(c == "push_front"){
			cin >> x;
			q[a].push_front(x);
		}
		if(c == "size"){
			cout << q[a].size() << endl;
		}
		if(!q[a].empty()){
			if(c == "pop_back"){
				q[a].pop_back();
			}
			if(c == "pop_front"){
				q[a].pop_front();
			}
			if(c == "front"){
				cout << q[a].front() << endl;
			}
			if(c == "back"){
				cout << q[a].back() << endl;
			}
		}	
	}
}