s:string; n,ans:longint;procedure init;begin readln(s); val(copy(s,pos(' ',s)+1,length(s)-pos(' ',s)),n); delete(s,pos(' ',s),length(s)-pos(' ',s)+1);end;procedure main;var i,j:longint;begin j:=1; for i:=length(s) downto 1 do begin if ord(s[i])-48>10 then begin ans:=ans+j*(ord(s[i])-55); j:=j*n; end else begin ans:=ans+j*(ord(s[i])-48); j:=j*n; end; end; writeln(ans);end;begin init; main;end.