def main():
    H, W = map(int, input().split())
    A = [list(input()) for _ in [0] * H]

    A[0][0] = 0
    for i in range(1, W):
        if A[0][i] == '.':
            A[0][i] = A[0][i-1] + 1
        else:
            A[0][i] = (A[0][i-1] + 1) * 2
    for i in range(1, H):
        if A[i][0] == '.':
            A[i][0] = A[i-1][0] + 1
        else:
            A[i][0] = (A[i-1][0] + 1) * 2
    for i in range(1, H):
        for j in range(1, W):
            if A[i][j] == '.':
                A[i][j] = min(A[i][j-1] + 1, A[i-1][j] + 1)
            else:
                A[i][j] = min(A[i][j-1] + 1, A[i-1][j] + 1) * 2
    print(A[H-1][W-1])


main()