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 "#".
n,m,x,y = map(int,input().split())
black = [0]
white = [0] 
for _ in range(n):
    s = input()
    for i in range(m):
        if s[i]=='#':
            black.append(back[-1]+1)
            white.append(white[-1])
        else:
            black.append(back[-1])
            white.append(white[-1]+1)

dp1 = [0]*(m+1)
dp2 = [0]*(m+1)

for i in range(x,m+1):
    for j in range(x,y+1):
        if i>=j:
            
            
            dp1[i]=min(dp1[i],dp2[i-j]+white[i]-white[i-j])
            dp2[i]=min(dp2[i],dp1[i-j]+black[i]-black[i-j]) 
        else:
            break 
print(min(dp1[m],dp2[m]))