#include<bits/stdc++.h>
#define INF 1e9
#define llINF 1e18
#define MOD 1000000007
#define pb push_back
#define mp make_pair 
#define F first
#define S second
#define ll long long
#define ull unsigned long long
#define vi vector<ll>
#define vvi vector<vi>
#define BITLE(n) (1LL<<((ll)n))
#define BITCNT(n) (__builtin_popcountll(n))
#define SUBS(s,f,t) ((s).substr((f)-1,(t)-(f)+1))
#define ALL(a) (a).begin(),(a).end()
using namespace std;
ll op[111111];
int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n,h,w;
  cin>>n>>h>>w;
  for(int i=0;i<n;i++){
    ll x;cin>>x;
    if(i%2 == 0){
      for(int j=i*w+x;j<(i+1)*w+x;j++)
	op[j] = 1;
    }else{
      for(int j=i*w-x;j<(i+1)*w-x;j++)
	op[j] = 1;
    }
  }
  ll ans=0;
  for(int i=0;i<n*w;i++){
    if(op[i] == 0)
      ans += h;
  }
  cout<<ans<<endl;
  return 0;
}

