#include <bits/stdc++.h>
#define Y8o "Fish"
#define maxn (int) 3e5 + 5
#define ll long long
#define pii pair<int, int>
#define gb(i, j) ((i >> j) & 1)
#define all(x) x.begin(), x.end()
#define _left id * 2, l, mid
#define _right id * 2 + 1, mid + 1, r
#define fi(i, a, b) for(int i = a; i <= b; i ++)
#define fid(i, a, b) for(int i = a; i >= b; i --)
#define f first
#define s second
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll GetRandom(ll l, ll r) {
return uniform_int_distribution<ll> (l, r) (rng);
}
void iof() {
ios_base::sync_with_stdio(0);
cin.tie(NULL), cout.tie(NULL);
if(fopen(Y8o".inp", "r"))
{
freopen(Y8o".inp", "r", stdin);
// freopen(Y8o".out", "w", stdout);
}
}
void ctime() {
cerr << "\n" << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
}
int n, Q; ll D;
ll a[maxn];
pii qr[maxn];
namespace sub1 {
void solve() {
fi(i, 1, Q) {
int l = qr[i].f, r = qr[i].s, notok = 0;
ll mi = 1e18, ans = 0;
fid(j, r, l) {
mi = min(mi, a[j]);
if(a[j] - mi != 0) {
ll du = a[j] % D, du2 = mi % D;
mi = mi - (du2 - du + D) % D;
// while(mi >= 0) {
// if((a[j] - mi) % D == 0) break;
// mi --;
// }
ans += (a[j] - mi) / D;
}
if(mi < 0) { notok = 1; break; }
}
cout << (notok ? -1 : ans) << '\n';
}
}
}
void solve() {
cin >> n >> D;
fi(i, 1, n) cin >> a[i] ;
cin >> Q ;
fi(i, 1, Q) cin >> qr[i].f >> qr[i].s;
if(n <= 3000) return sub1::solve(), void();
}
int main() {
iof();
int nTest = 1;
// cin >> nTest;
while(nTest --) {
solve();
}
ctime();
return 0;
}
