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 n = readln.chomp.to!size_t;
  auto s = readln.chomp;
  auto t = readln.chomp;

  writeln(s.zip(t).count!("a[0] != a[1]"));
}