type vector=array[0..750000] of longint;

var n:longint;
    s,t:ansistring;
    x:longint;

function qqq(s,t:ansistring):longint;
  var f:vector;
      k,i:longint;
      result:longint;
  begin
    result:=-1;
    f[1]:=0;
    k:=0;
    for i:=2 to length(s) do
      begin
        while (k>0) and (s[k+1]<>s[i]) do k:=f[k];
        if s[k+1]=s[i] then inc(k);
        f[i]:=k;
      end;
    k:=0;
    for i:=1 to length(t) do
      begin
        while (k>0) and (s[k+1]<>t[i]) do k:=f[k];
        if s[k+1]=t[i] then inc(k);
        if k=length(s)
          then
            begin
              result:=i+length(t);
              break;
            end;
      end;
    qqq:=result;
  end;

begin
  readln(n);
  readln(s);
  readln(t);
  x:=qqq(s,t+t);
  writeln(x mod length(s));
  readln;
end.