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 "#".
from math import inf
n, m, x, y = map(int, input().split())
w, a, b = [0] * 1100, [inf] * 1100, [inf] * 1100 
for i in range(n):
    s = input()
    for j in range(m):
        if(s[j] == '.'):
            w[j + 1] += 1 
for i in range(1, m + 1):
    w[i] += w[i - 1]
a[0], b[0] = 0, 0
for i in range(1, m + 1):
    for j in range(x, y + 1):
        if(i >= j):
            a[i] = min(a[i], w[i] - w[i - j] + b[i - j])
            b[i] = min(b[i], n * j - w[i] + w[i - j] + a[i - j]) 
print(min(a[m], b[m]))