import sys

sys.setrecursionlimit(25000)
input = sys.stdin.read().split()

h = int(input[0])
w = int(input[1])
cost_domino = int(input[2])
cost_square = int(input[3])

grid = []
idx = 4
for _ in range(h):
    grid.append(input[idx])
    idx += 1

free_count = 0
for r in range(h):
    for c in range(w):
        if grid[r][c] == '*':
            free_count += 1

if cost_domino >= 2 * cost_square:
    print(free_count * cost_square)
    sys.exit()

nodes_left = []
nodes_right = []
left_id = {}
right_id = {}

for r in range(h):
    for c in range(w):
        if grid[r][c] == '*':
            if (r + c) % 2 == 0:
                left_id[(r, c)] = len(nodes_left) + 1
                nodes_left.append((r, c))
            else:
                right_id[(r, c)] = len(nodes_right) + 1
                nodes_right.append((r, c))

L = len(nodes_left)
R = len(nodes_right)

adj_list = [[] for _ in range(L + 1)]

dr = [-1, 1, 0, 0]
dc = [0, 0, -1, 1]

for r, c in nodes_left:
    u = left_id[(r, c)]
    for i in range(4):
        nr, nc = r + dr[i], c + dc[i]
        if 0 <= nr < h and 0 <= nc < w and grid[nr][nc] == '*':
            v = right_id[(nr, nc)]
            adj_list[u].append(v)

assigned = [0] * (R + 1)

def match(node):
    if seen[node]:
        return False
    seen[node] = True
    for neighbor in adj_list[node]:
        if assigned[neighbor] == 0 or match(assigned[neighbor]):
            assigned[neighbor] = node
            return True
    return False

pairs_found = 0
for start in range(1, L + 1):
    seen = [False] * (L + 1)
    if match(start):
        pairs_found += 1
ans = pairs_found * cost_domino + (free_count - 2 * pairs_found) * cost_square
print(ans)