#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(),s.end()
#define rall(s) s.rbegin(),s.rend()
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ll n,d;
cin>>n>>d;
ll c[n+5];
for(ll i=1;i<=n;i++){
cin>>c[i];
}
ll q;
cin>>q;
ll a[n+5];
while(q--){
ll l,r;
cin>>l>>r;
for(ll i=l;i<=r;i++){
a[i]=c[i];
}
ll ans=0,tot=0;
for(ll i=l;i<=r;i++){
a[i]-=tot;
if(a[i]<0){
ans=-1;
break;
}
tot+=a[i]%d;
}
if(ans==-1){
cout<<ans<<"\n";
continue;
}
vector<ll>v;
for(ll i=r;i>=l;i--){
a[i]/=d;
ans+=a[i];
if(v.empty()||a[i]<a[v.back()]){
v.pb(i);
}
}
reverse(all(v));
ll last=l-1,sum=0;
for(ll i:v){
a[i]-=sum;
ans-=a[i]*(r-last);
last=i;
sum+=a[i];
}
cout<<ans<<"\n";
}
}
