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 "#".
inp = [int(i) for i in str(input()).split(" ")]
n = inp[0]  # row
m = inp[1]  # Column
x = inp[2]  # min block
y = inp[3]  # max block

grid = []
for i in range(n):
    grid.append(str(input()))

memo = {}


def fillSpace(lineNumber, length, pole):
    keys = [".", "#"]
    key = keys[pole]
    if lineNumber + (length - 1) > len(grid[0]) - 1:
        return 10000000

    colHeight = len(grid)
    total = 0
    for column in range(lineNumber, lineNumber + length):
        for row in range(0, colHeight):
            if grid[row][column] == key:
                total += 1
    return total


def barcode(lines, split, end, pole):
    if lines == end:
        return 0
    if lines > end:  # Illegal
        return 100000000

    if (lines, split, pole) in memo:
        return memo[(lines, split, pole)]

    total = []
    for blockLength in range(x, y + 1, 1):
        temp = fillSpace(lines, split, pole) + barcode(
            lines + split, blockLength, end, (pole + 1) % 2
        )
        total.append(temp)

    mn = min(total)
    memo[(lines, split, pole)] = mn
    return mn


print(min(barcode(0, 0, m, 0), barcode(0, 0, m, 1)))
