#include<bits/stdc++.h>
using namespace std;
void cleancin_n(){
	cin.ignore(numeric_limits<streamsize>::max(),'\n');
}
int a[1000001];
int check(int L,int R,int x,int y){
	bool mp[10001]={0};
	for(int i=L;i<=R;i++){
		mp[a[i]]=true;
	}
	for(int i=x;i<=y;i++){
		mp[a[i]]=false;
	}
	for(int i=1;i<=10001;i++){
		if(mp[i]==true){
			return false;
		}
	}
	return true;
}
int getans(int L,int R){
	int minn=INT_MAX-1;
	for(int x=L;x<=R;x++){
		for(int y=x;y<=R;y++){
		//	cout<<x<<" "<<y<<endl;
			if(check(L,R,x,y)){
				minn=min(minn,y-x+1);
				cout<<minn<<endl;
			}
		}
	}
	return (minn==INT_MAX-1)?-1:minn;
}
int l[10001],r[10001];
signed main(){
	int n,q;
	cin>>n>>q;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<=q;i++){
		cin>>l[i]>>r[i];
	}
	for(int i=1;i<=q;i++){
		cout<<l[i]<<" "<<r[i]<<endl;
		cout<<getans(l[i],r[i])<<endl;
	}
return 0;
}