This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
using namespace std;
#define task "Phenomena"
#define lb lower_bound
#define ub upper_bound
#define alll(v) (v).begin(),(v).end()
#define szz(v) (v).size()
#define fi first
#define se second
#define pb push_back
#define FOR(i,a,b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i,b,a) for (int i = (b), _a = (a); i >= _a; --i)
typedef long double ld;
typedef long long ll;
typedef pair<int,int> pii;
const int MOD=1000000007; /// 998244353
const int base=311; /// for hash actually
const int N=2e5+5;
ll st[4*N],lazy[4*N],n,q,s,t,a[N];
void down(int i, int l, int r)
{
    int t=lazy[i];
    st[i<<1]+=t;
    st[i<<1|1]+=t;
    lazy[i<<1]+=t;
    lazy[i<<1|1]+=t;
    lazy[i]=0;
}
void upd(int i, int l, int r, int u, int v, int val)
{
    if(u>r||v<l) return;
    if(u<=l&&r<=v)
    {
        lazy[i]+=val;
        st[i]+=val;
        return;
    }
    down(i,l,r);
    int mid=(l+r)>>1;
    upd(i<<1,l,mid,u,v,val);
    upd(i<<1|1,mid+1,r,u,v,val);
}
int get(int i, int l, int r, int p)
{
    if(l==r) return st[i];
    down(i,l,r);
    int mid=(l+r)>>1;
    if(p<=mid) return get(i<<1,l,mid,p);
    else return get(i<<1|1,mid+1,r,p);
}
void solved()
{
    cin>>n>>q>>s>>t;
    s=-s;
    ll ans=0;
    ++n;
    FOR(i,1,n)
    {
        cin>>a[i];
        upd(1,1,n,i,i,a[i]);
    }
    FOR(i,1,n-1)
    {
        if(a[i]<a[i+1]) ans+=s*(a[i+1]-a[i]);
        else ans+=t*(a[i]-a[i+1]);
    }
    while(q--)
    {
        int l,r,x;
        cin>>l>>r>>x;
        ++l,++r;
        int p1=get(1,1,n,l-1), p2=get(1,1,n,l);
        if(l>1&&p1<p2) ans-=s*(p2-p1);
        else ans-=t*(p1-p2);
//        cout<<s*(p2-p1)<<endl;s
        p1=get(1,1,n,r), p2=get(1,1,n,r+1);
        if(r<n&&p1<p2) ans-=s*(p2-p1);
        else ans-=t*(p1-p2);
//        cout<<ans<<endl;
        upd(1,1,n,l,r,x);
        p1=get(1,1,n,l-1), p2=get(1,1,n,l);
        if(l>1&&p1<p2) ans+=s*(p2-p1);
        else ans+=t*(p1-p2);
        p1=get(1,1,n,r), p2=get(1,1,n,r+1);
        if(r<n&&p1<p2) ans+=s*(p2-p1);
        else ans+=t*(p1-p2);
        cout<<ans<<'\n';
        /*FOR(i,1,n) cout<<get(1,1,n,i)<<' ';
        cout<<endl;*/
    }
}
int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    if(fopen(task".inp","r"))
    {
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    solved();
}
Compilation message (stderr)
foehn_phenomena.cpp: In function 'int main()':
foehn_phenomena.cpp:99:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   99 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foehn_phenomena.cpp:100:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  100 |         freopen(task".out","w",stdout);
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