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 "#".
def main(arr,x,y):

    col=[[0 for i in range(2)] for j in range(len(arr[0]))]

    for i in range(len(arr[0])):
        for j in range(len(arr)):
            if arr[j][i]=='.':

                col[i][0]+=1 
            else:
                col[i][1]+=1 
    dp=[[[float('inf') for k in range(2)] for j in range(y+1)] for i in range(len(arr[0]))]

    a=dp[0][1][0]=col[0][0]
    b=dp[0][1][1]=col[0][1]
    prev_min=[b,a]
    
    for i in range(1,len(dp)):
        curr_min=[float('inf'),float('inf')]
        for j in range(1,len(dp[0])):
            for k in range(2):
                valid=x<=j and j<=y and j<=(i+1)
                if  valid and j>1:
                    dp[i][j][k]=col[i][k^1]+dp[i-1][j-1][k]
                    
                elif valid and j==1:
                    
                        
                    dp[i][j][k]=col[i][k^1]+prev_min[k^1]
                
                curr_min[k]=min(curr_min[k],dp[i][j][k])
      
        prev_min=curr_min 
    
    ans=float('inf')
    
    for j in range(len(dp[0])):
        for k in range(2):
            ans=min(ans,dp[-1][j][k])
    return ans 

n,m,x,y=list(map(int,input().split()))
arr=[]
for i in range(n):
    arr.append([c for c in input()])
print(main(arr,x,y))


                


