//# pragma GCC optimize(2)
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
constexpr int N = 250 * 2 + 2 + 7;
constexpr int M = 250 * 250 + 250 * 2 + 7;

template <typename A, typename B>
bool smax(A &a, const B &b) { return a < b ? a = b, 1 : 0; }
template <typename A, typename B>
bool smin(A &a, const B &b) { return b < a ? a = b, 1 : 0; }

int n,m,k;
int S,T;

char s[N][N];
int col[N],row[N];

int h[N],e[M<<1],ne[M<<1],f[M<<1],tot;

void add(int u,int v, int x)
{
    e[tot] = v,ne[tot] = h[u],f[tot] = x,h[u] = tot++;
    e[tot] = u,ne[tot] = h[v],f[tot] = 0,h[v] = tot++;
}


int dep[N],cur[N],gap[N],q[N];
int nod;

void bfs()
{
    int hd = 0, tl = 0;
    q[++tl] = T, ++gap[dep[T] = 1];

    while(hd < tl)
    {
        int u = q[++hd];
        //cout << u << endl;

        for(int i = h[u];~i;i = ne[i])
        {
            int v = e[i];
            if(!dep[v] && f[i^1])
            {
                dep[v] = dep[u] + 1;
                gap[dep[v]]++;
                q[++tl] = v;
            }
        }
    }
}

int dfs(int u,int a)
{
    if(u == T || a == 0) return a;

    int flow = 0,tmp;

    for(int& i = cur[u];~i;i = ne[i])
    {
        int v = e[i];
        if(dep[v] == dep[u] - 1 && (tmp = dfs(v,min(a,f[i]))))
        {
            flow += tmp;
            f[i] -= tmp;
            f[i^1] += tmp;
            a -= tmp;

            if(a == 0)
            {
                return flow;
            }
        }
    }

    --gap[dep[u]];
    if(!gap[dep[u]]) gap[S] = nod + 1;
    ++gap[++dep[u]];

    return flow;
}

int ISAP()
{
    static int res = 0;
    bfs();
    while(dep[S] <= nod)
    {
        memcpy(cur,h,sizeof(*cur)*nod);
        res += dfs(S,inf);
    }

    return res;
}

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    #ifndef ONLINE_JUDGE
    freopen("in.txt", "r+", stdin);
    freopen("out.txt", "w+", stdout);
    #endif

    int c, d, mxk = 0, sum = 0;
    cin >> n >> m >> c >> d;
    for (int i = 1; i <= n; ++i)
    {
        cin >> (s[i] + 1);
        for (int j = 1; j <= m; ++j)
            s[i][j] = s[i][j] == '.', row[i] += s[i][j], col[j] += s[i][j], smax(mxk, col[j]);
        smax(mxk, row[i]), sum += row[i];
    }

    S = 0, T = n + m + 1 ,nod = T + 1;

    for(int i = S;i<=T;i++)
    {
        h[i] = -1;
    }
    for (int i = 1; i <= n; ++i)
        add(S, i, 0);
    for (int i = 1; i <= m; ++i)
        add(i + n, T, 0);
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            if (s[i][j])
                add(i, j + n, 1);

    ll ans = LLONG_MAX;
    for (int k = 0; k <= mxk; ++k)
    {
        if (k)
        {
            memset(gap, 0, sizeof(*gap) * nod);
            memset(dep, 0, sizeof(*dep) * nod);
            for (int i = 0; i < n; ++i)
                ++f[i * 2];
            for (int i = 0; i < m; ++i)
                ++f[(i + n) * 2];
        }

        smin(ans, (ll)c * k + (ll)d * (sum - ISAP()));
    }
    cout << ans;

    return 0;

}