program fibonachi;

{$APPTYPE CONSOLE}
uses
  SysUtils;
type long=array[0..10000] of integer;

var f1,f2,f3:string;
n,i:integer;

function s(a,b:long):long;
var c:long;
os,i:integer;
begin
if a[0]>b[0] then c[0]:=a[0] else c[0]:=b[0];
os:=0;
for i:=1 to c[0] do begin
c[i]:=(a[i]+b[i]+os) mod 10;
os:=(a[i]+b[i]+os) div 10;
end;
if os>0 then begin c[0]:=c[0]+1;c[c[0]]:=os;end;
s:=c;
end;


function s3(s1,s2:string):string;
var s4:string;
ost,a,i:integer;
begin
while length(s1)<>length(s2) do
if   length(s1)<length(s2)  then s1:='0'+s1 else s2:='0'+s2;
s4:='';
ost:=0;
for i:=length(s1) downto 1 do  begin
a:=(ord(s1[i])-ord('0')+ord(s2[i])-ord('0')+ost)mod 10;
ost:=(ord(s1[i])-ord('0')+ord(s2[i])-ord('0')+ost)div 10;
s4:=inttostr(a)+s4 ;
end;
if ost >0 then s4:=inttostr(ost)+s4 ;
s3:=s4;
end;





begin
readln(n);
f1:='1'; f2:='1';

//f1[0]:=1;f1[1]:=1;
//f2[0]:=1;f2[1]:=1;


for i:=3 to n+1 do begin
f3:=s3(f1,f2);
//f3:=s(f1,f2);
f1:=f2;
f2:=f3;
end;

writeln(f3);
//for i:=f3[0] downto 1 do write(f3[i]);
writeln;
readln;
end.