#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define sz(x) (int)x.size()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define fi first
#define se second
#define cmin(a, b) a=min(a, b)
#define cmax(a, b) a=max(a, b)
void solve();
signed main() {
ios::sync_with_stdio(0); cin.tie(0);
solve();
return 0;
}
int n, k, q;
vector<int> a;
void solve() {
cin >> n >> k;
a.resize(n); for (auto &u: a) cin >> u;
cin >> q;
while (q--) {
int l, r; cin >> l >> r; l--, r--;
auto base=a;
int nb=0, ans=0, left=0;
for (int i=l; i<=r; i++) {
if (a[i]<nb) { ans=-1; break; }
nb+=(a[i]-nb)%k;
a[i]-=nb;
ans+=a[i]/k;
}
int mini=r;
vector<int> nxt(n);
for (int i=r; i>=l; i--) {
if (a[i]<a[mini]) mini=i;
nxt[i]=mini;
}
nb=0;
for (int i=l; i<=r; i++) {
if (a[nxt[i]]-nb) {
ans-=((a[nxt[i]]-nb)/k)*(r-i+1);
nb=a[nxt[i]];
i=nxt[i];
}
}
cmax(ans, -1LL);
cout << ans << endl;
a=base;
}
}
