#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <climits>
#include <vector>
#include <map>
#include <set>
#include <list>
#include <stack>
#include <queue>
#include <algorithm>
#include <iostream>
#include <string>

#define REP(i,n) for(long long i=0;i<n;++i)
#define REPR(i,n) for(long long i=n;i>=0;--i)
#define REPI(itr,v) for(auto itr=v.begin();itr!=v.end();++itr)
#define REPIR(itr,v) for(auto itr=v.rbegin();itr!=v.rend();++itr)
#define FOR(i,a,b) for(long long i=a;i<b;++i)
#define SORT(v,n) sort(v, v+n)
#define SORTV(v) sort(v.begin(), v.end())
#define ALL(v) v.begin(),v.end()
#define llong long long
#define INF 999999999
#define SUR 1000000007
#define pb push_back
#define pf push_front
#define MP make_pair
#define SV(v) {for(long long sitr=0;sitr<v.size();++sitr){cin>>v[sitr];}}

int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};

using namespace std;

typedef pair<int,int> pii;

bool windows[100*100][100] = {};

int main(){

  int n, h, w;
  scanf("%d %d %d", &n, &h, &w);
  REP(i,n){
    int x;
    scanf("%d", &x);
    for(int j = 0; j < w; ++j){
      for(int k = 0; k < h; ++k){
        if(i % 2 == 0){
          windows[i*w + j + x][k] = true;
        }else{
          windows[i*w + j - x][k] = true;
        }
      }
    }
  }

  llong ans = 0;
  REP(i,w*n){
    REP(j,h){
      if(!windows[i][j]){
        ans++;
      }
    }
  }

  printf("%lld\n", ans);
  return 0;
}


