import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
// dfmt on

void main()
{
    long N = lread();
    auto S = sread();
    auto T = sread();
    outer: foreach_reverse (i; 0 .. N + 1)
    {
        foreach (j; 0 .. i)
        {
            if (S[N - i + j] != T[j])
                continue outer;
        }
        writeln(2 * N - i);
        return;
    }
}
