program doisprezece;
var i,s,n:integer;
function fib(k:integer):integer;
begin
if (k=1) or (k=2) then fib:=1
else fib:=fib(k-1)+fib(k-2);
end;
begin
repeat
write('introduceti un nr impar, n ');
readln(n);
until n mod 2=1;
s:=0;
for i:=1 to n do if i mod 2=1 then s:=s+fib(i);
writeln(s);
readln;
end.