You've got an *n* × *m* pixel picture. Each pixel can be white or black. Your task is to change the colors of as few pixels as possible to obtain a barcode picture.

A picture is a barcode if the following conditions are fulfilled: 
 -  All pixels in each column are of the same color. -  The width of each monochrome vertical line is at least *x* and at most *y* pixels. In other words, if we group all neighbouring columns of the pixels with equal color, the size of each group can not be less than *x* or greater than *y*.
The first line contains four space-separated integers *n*, *m*, *x* and *y* (1 ≤ *n*, *m*, *x*, *y* ≤ 1000; *x* ≤ *y*).

Then follow *n* lines, describing the original image. Each of these lines contains exactly *m* characters. Character "." represents a white pixel and "#" represents a black pixel. The picture description doesn't have any other characters besides "." and "#".
def solve(p, s, l):
    global x, y
    if p < s:
        if x <= l <= y:
            return p, l+1
        else:
            return s, 1
    elif s <= p:
        if x <= l <= y:
            return s, l+1
        else:
            return p, 1
    # else


n, m, x, y = map(int, input().split())
l = [[] for i in range(m)]
v = []
for _ in range(n):
    e = list(input())
    for idx, i in enumerate(e):
        l[idx].append(i)

for i in l:
    a = i.count('.')
    v.append((a, n-a))
del l

# print(v)
ans, l =0, 1
for p, s in v:
    a, l = solve(p, s, l)
    ans += a
    # print(a, l)
print(ans)