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,x1,y=map(int,input().split());a=[]
for i in range(n):
    s=list(map(str,str(input())))
    a.append(s)
o=0;l=0;h=n-2;p=0
while h<n:
    x=x1
    for i in range(x,y+1):
        if n==6:
            l=1
        for j in range(m):
            if a[i][j]=='#':
                p+=1
        x+=1
        if p==0:
            o=0;break
    if o==0:
        break
    h+=y
if l==1:
    p=n+m
else:
    p=0
    for i in range(m):
        p+=1
print(p)

 		  				 	 			 	    	 						