单调队列求助 WA

#include<bits/stdc++.h>
using namespace std;
int a[2000001];
deque<pair<int,int>>q;
int main()
{
    int n,m,i;
    cin>>n>>m;
    for(i=1;i<=n;i++)
    {
        cin>>a[i];
    }
    cout<<"0"<<endl;
    for(i=1;i<=n;i++)
    {
        while(q.empty()==0&&q.front().first>a[i])
        {
            q.pop_front();
        }
        q.push_front(make_pair(a[i],i));
        while(q.empty()==0&&q.back().second<=i-m)
        {
            q.pop_back();
        }
        if(i>=m)
        {
            cout<<q.back().first<<endl;
        }
    }
    return 0;
}