% https://latexeditor.lagrida.com/
\text{lev}(a,b) = |a| & \quad \text{когато } |b| = 0 \\
\text{lev}(a,b) = |b| & \quad \text{когато } |a| = 0 \\
\text{lev}(a,b) = \text{lev}(a[1..], b[1..]) & \quad \text{когато } a[0] = b[0] \\
\text{lev}(a,b) = 1 + \min(\text{lev}(a, b[1..]),\text{lev}(a[1..], b),\text{lev}(a[1..], b[1..])) & \quad \text{иначе} \\