Typo

Author: lengyijun

content/computability/computability-theory/reducibility.tex

@@ -54,7 +54,7 @@
 \[
 x \in A \quad \text{if and only if} \quad f(x) \in B.
 \]
-If such a reduction $f$ existss, we say that $A$ is \emph{many-one
+If such a reduction $f$ exists, we say that $A$ is \emph{many-one
 reducible} to~$B$, written $A \leq_m B$. If $A$ is many-one reducible
 to $B$ and vice-versa, then $A$ and $B$ are said to be \emph{many-one
 equivalent}, written $A \equiv_m B$.