#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<ll> vi;
typedef pair<ll, ll> pi;
#define FOR(i, j, k) for (ll i = j; i < (ll) k; ++i)
#define FORD(i, j, k) for (ll i = j; i >= (ll) k; --i)
#define nl "\n"
#define sp " "
#define all(x) (x).begin(), (x).end()
#define sc second
#define fr first
#define pb emplace_back
void solve()
{
ll n, q, s, t;
cin >> n >> q >> s >> t;
ll a[n + 1];
FOR(i, 0, n + 1)
cin >> a[i];
auto calc = [&]() {
return (a[0] - a[n]) * s;
};
while(q--) {
int l, r, v;
cin >> l >> r >> v;
if(r == n)
a[r] += v;
cout << calc() << nl;
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t = 1;
// cin >> t;
while (t--)
{
solve();
}
}
