# curly braces and nested array

I have to write the equation written in image, i use array to create the first big curly brace, now I've tried to nest another array to write second curly brace but I get error.

This is the code that gave me error:

DTW(A,B)=\left\{ \begin{array}{l}
0 \quad \text{se $n$=0 ed $m$=0}\\
\infty \quad \text{se $n$=0 o $m$=0}\\
d(H(A),H(B))+\min\left\{
\begin{array}{1}
a\\
b\\
c\\
\end{array}
\right.
\end{array} \right.


How can I write this equation? Thank you.

-
Please give the code giving the error. –  Stephan Lehmke May 2 '12 at 15:25
The {1} after the inner \begin{array} should be {l} (an "ell", not a "one"). The error was Illegal character in array arg. –  egreg May 2 '12 at 15:33
Not tested, but you have 1 (one) instead of l (ell) in the second array spec. - Gah, Ninja'd. –  Stephan Lehmke May 2 '12 at 15:33

You have a typo in your inner array

change

     \begin{array}{1}
%%%


to

   \begin{array}{l}
%%%

-
To give you another possibility using cases from amsmath or mathtools.
\documentclass{article}
$$DTW(A,B)=\begin{cases} 0 \quad \phantom{\infty}\text{if}\,\, n=0 \,\,\text{and}\,\, m=0 \\ \infty \quad \phantom{0} \text{if}\,\, n=0 \,\,\text{and}\,\, m=0 \\ {d(H(A),H(B))+\min \begin{cases} a\\ b\\ c\\ \end{cases}} \end{cases}$$