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

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


main()