TLE，70pts，玄关求条

#include<bits/stdc++.h>
using namespace std; 
int n,q;
int lg[200010],f[200008][48];
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 main(){
	n=read();q=read();
	for(int i=2;i<=n;i++) lg[i]=lg[i>>1]+1;
	for(int i=1;i<=n;i++) f[i][0]=read();
	for(int j=1;j<=21;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]);
		}
	}
	while(q--){
		int x,y;
		x=read(),y=read();
		int l=lg[y-x+1];
		cout<<max(f[x][l],f[y-(1<<l)+1][l])<<endl;
	} 
	return 0;
}