Inserting Curly Brackets in equations

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documentclass[12pt]{article}
usepackage{amsmath}
begin{document}
begin{equation*}
begin{cases}
  c colon {1, dots, n} rightarrow {1, dots, n} text{ such that}      
  c(a_i) = a_{i+1}  text{ for $1le i<l$}
  c(a_l) = a_1
end{cases}
end{equation*}
end{document}