rt,

#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define per(i,a,b) for(int i=a;i>=b;i--)
#define endl '\n'
#define pii pair<int,int>
#define fi first
#define se second
typedef long long ll;
typedef unsigned long long ull;
typedef double lf;
typedef long double ld;
using namespace std;
struct query{
	ll l,r;
}qu[50005];
ll n,q,f[1048576],a[50005],ans[50005],g[50005];
signed main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n>>q;
	rep(i,1,1048576)
		f[i]=f[i-1]^i;
	rep(i,1,n)
		cin>>a[i];
	rep(i,1,q)
		cin>>qu[i].l>>qu[i].r;
	rep(i,1,n){
		per(j,i,1)
			g[j]=max(max(g[j+1],g[j]),f[max(a[i],a[j])]^f[min(a[i],a[j])-1]);
		rep(j,1,q)
			if(qu[j].r==i)
				ans[j]=g[qu[j].l];
	} 
	rep(i,1,q)
		cout<<ans[i]<<endl; 
	return 0;
}
/*

*/
不是O2的锅