var i,n,j,des:integer;
a,b,c:array[0..100000] of integer;
f:text;
begin
assign(f,'signal.dat');
reset(f);
readln(f,n);
close(f);

a[0]:=1;a[1]:=5;
b[0]:=1;b[1]:=8;
for j:=5 to n do begin

         if a[0]>b[0] then c[0]:=a[0] else c[0]:=b[0];
         des:=0;
         for i:=1 to c[0] do begin
                 c[i]:=(a[i]+b[i]+des) mod 10;
                 des:=(a[i]+b[i]+des) div 10;
                      end;

                      if des>0 then begin c[0]:=c[0]+1;c[c[0]]:=des;end;

                      for i:=1 to b[0] do a[i]:=b[i];
                      a[0]:=b[0];
                      for i:=1 to c[0] do b[i]:=c[i];
                      b[0]:=c[0];



end;
assign(f,'signal.sol');
rewrite(f);
for i:=c[0] downto 1 do write(f,c[i]);
writeln(f);
close(f);

end.