#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,q;
	cin>>n>>q;
	bool a;
	int b[1000005]={};
	for(int i=1;i<=n;i++){
		cin>>a;
		b[i]=b[i-1]+a;
	}
	int l,r,k;
	int x;
	for(int i=1;i<=q;i++){
		cin>>l>>r>>k;
		if(k>r-l){printf("-1\n");continue;}
		x=b[r]-b[l-1];
		if(abs(k-x)!=1||r-l+1!=x)printf("%d\n",abs(k-x));
		else printf("%d\n",abs(k+1-x));
	}
	return 0;
}