1=0 Part I

Here is my attempt to demonstrate that $1=0$.

1) $0=0$

2) $0=1-1$

3) $n\cdot 0=n(1-1)$, $n$ is a big natural number.

4) $0=\underset { n\text{ times} }{ \underbrace { (1-1)+(1-1)+...+(1-1) } }$

5) $0=1-1+1-\cdots -1$

6) $0=1-(1-1+1-1+\cdots)$

7) $0=1-((1-1)+(1-1)+\cdots +(1-1))$

8) $0=1-(0+0+\cdots + 0)$

9) $0=1$

In which step is the first error committed?