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 sys import stdin
input = stdin.readline
n,m,x,y=map(int,input().split())
A=[input() for i in range(n)]
Z=[]
for j in range(m):
    cnt=0
    for i in range(n):
        if A[i][j]=="#":
            cnt+=1
    Z.append(cnt)
# print(Z)
def rec(last,streak,i):
    if i==m:
        return 0 if x<=streak<=y else 10**10
    if last==1:
        if streak<x:
            return n-Z[i]+rec(1,streak+1,i+1)
        elif x<=streak<y:
            return min(n-Z[i]+rec(1,streak+1,i+1),Z[i]+rec(0,1,i+1)) 
        elif streak==y:
            return Z[i]+rec(0,1,i+1)
    else:
        if streak<x:
            return Z[i]+rec(0,streak+1,i+1)
        elif x<=streak<y:
            return min(n-Z[i]+rec(1,1,i+1),Z[i]+rec(0,streak+1,i+1)) 
        elif streak==y:
            return n-Z[i]+rec(1,1,i+1)


ans=min(n-Z[0]+rec(1,1,1),Z[0]+rec(0,1,1))
# if A==["."*m]*n:
#     ans=n*x
print(ans)