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 "#".
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
for _ in range(1):
    n,m,x,y=[int(x) for x in input().split()]
    arr=[]
    for i in range(n):
        s=input()
        arr.append(s[:-1])
    temp=[]
    for i in range(m):
        c=0
        for j in range(n):
            if arr[j][i]=='#':
                c+=1
        temp.append(c)
    #print(temp)
    d={}
    def helper(curr,sz,sy):
        if curr==m:
            return 0
        if (curr,sz,sy) in d:
            return d[(curr,sz,sy)]
        if sz<x:
            if sy=='#':
                ans=temp[curr]+helper(curr+1,sz+1,sy)
            else:
                ans=n-temp[curr]+helper(curr+1,sz+1,sy)
        elif sz==y:
            if sy=='#':
                ans=n-temp[curr]+helper(curr+1,1,'.')
            else:
                ans=temp[curr]+helper(curr+1,1,'#')
        else:
            if sy=='#':
                ans=min(temp[curr]+helper(curr+1,sz+1,sy),n-temp[curr]+helper(curr+1,1,'.'))
            else:
                ans=min(n-temp[curr]+helper(curr+1,sz+1,sy),temp[curr]+helper(curr+1,1,'#'))
        d[(curr,sz,sy)]=ans
        return ans
    print(min(helper(0,0,'#'),helper(0,0,'.')))
            