import std.algorithm, std.array, std.container, std.range, std.bitmanip;
import std.numeric, std.math, std.bigint, std.random, core.bitop;
import std.string, std.regex, std.conv, std.stdio, std.typecons;

void main()
{
  auto rd = readln.split.map!(to!size_t);
  auto n = rd[0], m = rd[1];
  auto s = readln.chomp;
  auto t = readln.chomp;

  writeln(levenshteinDistance(s, t));
}