#include <bits/stdc++.h>
using namespace std;
const long double eps = 1e-9;
typedef long long ll;
typedef long double ld;
const int mod = 998244353;
struct Mint
{
int val;
Mint(int x = 0)
{
val = x % mod;
}
Mint(long long x)
{
val = x % mod;
}
Mint operator+(Mint oth)
{
return val + oth.val;
}
Mint operator*(Mint oth)
{
return 1LL * val * oth.val;
}
Mint operator-(Mint oth)
{
return val - oth.val + mod;
}
Mint fp(Mint a, long long n){
Mint p = 1;
while(n){
if(n & 1){
p = p * a;
}
a = a * a;
n /= 2;
}
return p;
}
Mint operator/(Mint oth){
Mint invers = fp(oth, mod - 2);
return 1LL * val * invers.val;
}
friend ostream& operator << (ostream& os, const Mint& lol){
os << lol.val;
return os;
}
};
struct AINT{
vector<ll> aint, lazy;
AINT(int n){
aint.assign(n * 4 + 1, 0);
lazy.assign(n * 4 + 1, 0);
}
void update(int v, int tl, int tr, int l, int r, int val){
if(lazy[v]){
aint[v] += lazy[v];
if(tl != tr){
lazy[v * 2] += lazy[v];
lazy[v * 2 + 1] += lazy[v];
}
lazy[v] = 0;
}
if(l <= tl && r >= tr){
aint[v] += val;
if(tl != tr){
lazy[v * 2] += val;
lazy[v * 2 + 1] += val;
}
return;
}
if(l > tr || r < tl) return;
int tm = (tl + tr) / 2;
update(v * 2, tl, tm,l,r,val);
update(v * 2 + 1, tm + 1, tr, l, r,val);
aint[v] = aint[v * 2] + aint[v * 2 + 1];
}
ll query(int v, int tl, int tr, int l, int r){
if(lazy[v]){
aint[v] += lazy[v];
if(tl != tr){
lazy[v * 2] += lazy[v];
lazy[v * 2 + 1] += lazy[v];
}
lazy[v] = 0;
}
if(l <= tl && r >= tr) return aint[v];
if(l > tr || r < tl) return 0;
int tm = (tl + tr) / 2;
return query(v * 2, tl, tm,l, r) + query(v * 2 + 1, tm + 1, tr, l, r);
}
};
int red =0;
int ______________________________________________________________________________________________________________________________________________;
void solve(){
ll n, d;
cin >> n >> d;
vector<ll> v(n + 1), ct(n + 1);
for(int i = 1; i <= n; i++){
cin >> v[i];
}
// vector<vector<pair<int,int>>> lr(n + 1);
// int q;
// cin >> q;
// for(int i = 1; i <= q; i++){
// int l,r;
// cin >> l >> r;
// lr[r].push_back({l,i});
// }
// AINT aint(n + 1);
// for(int i = 1; i <= n; i++){
// aint.update(1,1,n, i,i, v[i]);
// }
// stack<ll> s;
// for(int i = 1; i <= n; i++){
// while(s.size() && v[s.top()] > v[i]){
// aint.update(1,1,n, s.top(), n, ct[s.top()]);
// s.pop();
// }
// if(s.size()){
// ct[i] = v[i] - v[s.top()];
// aint.update(1,1,n, i, n, -ct[i]);
// }else{
// ct[i] = v[i];
// aint.update(1,1,n, 1, n, -ct[i]);
// }
// s.push(i);
// for(auto j : lr[i]){
// }
// }
int q;
cin >> q;
while(q--){
int l,r;
cin >> l >> r;
stack<int> s;
vector<ll> mars(n + 2), minim(n + 2, 1e18);
ll tl = 0;
for(int i = r; i >= l; i--){
minim[i] = min(minim[i + 1], v[i]);
}
ll ans = 0;
ll m1 = 1e18;
ll sm = 0;
for(int i = l; i <= r; i++){
ll pl = (v[i] - tl + d) %d;
if(tl + pl > minim[i]){
ans = -1;
break;
}else{
tl += pl;
m1 = min(m1, (v[i] - tl));
sm += (v[i] - tl);
}
}
if(!ans){
cout << (ll)(sm - (ll)(r-l+1)*m1)/d - (d == 1 ? v[r] - m1 : 0) << '\n';
}else{
cout << ans << '\n';
}
}
}
int32_t main(){
cin.tie(0)->sync_with_stdio(0);
int t = 1;
if(red) cin >> t;
while(t--){
solve();
}
}
/*
10
10 4
10 2
9 10
4 3
5 1
5 8
7 1
6 8
1 10
15, 12, 9, 3, 0
*/
