#include <bits/stdc++.h>
#define int int64_t
signed main() {
int n, d;
std::cin >> n >> d;
std::vector<int> a(n + 1);
for(int i = 1; i <= n; i++) {
std::cin >> a[i];
}
int q;
std::cin >> q;
while(q--) {
int l, r;
std::cin >> l >> r;
if(is_sorted(a.begin() + l, a.begin() + r + 1)) {
std::cout << 0 << "\n";
continue;
}
std::vector<int> f = a;
int can = 1;
int ans = 0;
for(int i = r - 1; i >= l; i--) {
if(f[i] < f[i + 1]) {
continue;
}
int cnt = (f[i] - f[i + 1] + d - 1) / d;
f[i] = f[i + 1] - d + f[i] % d;
ans += cnt;
if(f[i] < 0) {
can = 0;
break;
}
}
std::cout << (can == 1 ? ans : - 1) << "\n";
}
}
