rt，感觉复杂度是对的。

#include<bits/stdc++.h>
using namespace std;
//No,commander.
inline int read()
{
	int x=0,f=1;char ch=getchar();
	while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
	while (ch>='0'&&ch<='9'){x=x*10+ch-48;ch=getchar();}
	return x*f;
}
int lg[100007]; 
int n,m;
int f[100007][22];
signed main(){
	n=read(),m=read();
	lg[0]=-1;
    for(int i=1;i<=n;i++){
		f[i][0]=read();
		lg[i]=lg[i>>1]+1;
	}
    for(int j=1;j<=lg[n];j++){
    	for(int i=1;i+(1<<j)-1<=n;i++){
			f[i][j]=max(f[i][j-1],f[i+(1<<(j-1))][j-1]);
		}
	}
	for(int i=1;i<=m;i++){
		int l,r;
		l=read(),r=read();
		int u=lg[r-l+1];
		cout<<max(f[l][u],f[r-(1<<u)+1][u])<<endl;
	}
	return 0;
}