#include <bits/stdc++.h>
using namespace std;
namespace std {
template <int D, typename T>
struct Vec : public vector<Vec<D - 1, T>> {
static_assert(D >= 1, "Dimension must be positive");
template <typename... Args>
Vec(int n = 0, Args... args) : vector<Vec<D - 1, T>>(n, Vec<D - 1, T>(args...)) {}
};
template <typename T>
struct Vec<1, T> : public vector<T> {
Vec(int n = 0, T val = T()) : std::vector<T>(n, val) {}
};
/* Example
Vec<4, int64_t> f(n, k, 2, 2); // = f[n][k][2][2];
Vec<2, int> adj(n); // graph
*/
template <class Fun>
class y_combinator_result {
Fun fun_;
public:
template <class T>
explicit y_combinator_result(T&& fun) : fun_(std::forward<T>(fun)) {}
template <class... Args>
decltype(auto) operator()(Args&&... args) {
return fun_(std::ref(*this), std::forward<Args>(args)...);
}
};
template <class Fun>
decltype(auto) y_combinator(Fun&& fun) {
return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun));
}
/* Example
auto fun = y_combinator([&](auto self, int x) -> void {
self(x + 1);
});
*/
} // namespace std
#define endl "\n"
void solve() {
int n; long long d; cin >> n >> d;
vector<long long> c(n);
for (int i = 0; i < n; i++) {
cin >> c[i];
}
int q; cin >> q;
while (q--) {
int l, r; cin >> l >> r;
l--; r--;
long long last = c[r];
long long ans = 0;
for (int i = r - 1; i >= l; i--) {
long long cur = c[i];
if (cur > last) {
long long tmp = (cur - last + d - 1) / d;
ans += tmp;
cur -= tmp * d;
if (cur < 0) {
ans = -1;
break;
}
}
last = cur;
}
cout << ans << endl;
}
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while (t--) {
solve();
}
}
