Var
   ch: char;
   r,s: string;
   i,j,l,n,p: longint;

Begin
     readln(input,n,ch,s);
     l:= length(s);
     j:= 1; p:= 1;
     for i:= 1 to length(s) do
         begin
         r[p]:= s[i];
         Inc(p,n);
         if (p>l) then
            begin
            Inc(j);
            p:= j;
            end;
         end;
     r[0]:= s[0];
     writeln(output,r);
End.