import std.stdio,
       std.conv,
       std.string,
       std.range,
       std.math,
       std.algorithm;

void main()
{
    auto n = readln.strip.to!int;
    auto S = readln.strip;
    auto T = readln.strip;

    //zip(S, T).count!"a[0]!=a[1]".writeln;
    S.levenshteinDistance(T).writeln;
}