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| #include <bits/stdc++.h>
using namespace std;
const double eps = 1e-10;
const double pi = 3.1415926535897932384626433832795;
const double eln = 2.718281828459045235360287471352;
#define f(i, a, b) for (int i = a; i <= b; i++)
#define scan(x) scanf("%d", &x)
#define mp make_pair
#define pb push_back
#define lowbit(x) (x&(-x))
#define fi first
#define se second
#define SZ(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define summ(a) (accumulate(all(a), 0ll))
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
using ll=long long;
ll n,m,x,y,a[(int)2e5+9],ans,lstd,lstw=-10086;
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m>>x>>y;
for(int i=1;i<=m;++i)cin>>a[i];
a[m+1]=n+1;
for(int i=1;i<=m+1;++i){
ll wk=a[i]-1-a[i-1];
if(a[i-1]-lstw==1&&wk+lstd>y){
wk-=(y-lstd+1),ans+=1;
ans+=wk/(y+2ll)*2ll,wk%=(y+2ll);
if(wk>lstd){
ans+=1,wk-=(lstd+1);
}
}
if(wk>x){
if(2ll*x<=y){
ans+=wk/(x+1ll),wk=wk%(x+1ll);
if(wk==0)lstw=a[i]-2;
else lstw=a[i]-1;
}else{
ans+=wk/(y+2ll)*2ll,wk%=(y+2ll);
if(wk==0)lstw=a[i]-2;
else{
if(wk>x){
ans+=1,wk-=(x+1);
if(wk==0)lstw=a[i]-2;
else lstw=a[i]-1;
}else lstw=a[i]-1;
}
}
}else lstw=a[i]-1;
lstd=wk;
}
cout<<ans;
return 0;
}
|