为什么0分啊？蒟蒻求助

#include <cstdio>
int main(){
  int n, m, a[2000001];
  scanf("%d%d",&n,&m);
  for (int i = 1; i <= n; i++){
    scanf("%d",&a[i]);
  }
  int head = 0, tail = 0, q[2000001] = {0};
  for (int i = 0; i <= n; i++){
    while (head <= tail && a[q[tail ]] >= a[i]){
      tail--;
    }
    q[++tail] = i;
    while (q[head ] <= i - m){
      head++;
    }
    printf("%d\n",a[q[head]]);
  }
  return 0;
}