function fibonacci(n: integer): integer;
var
    a, b, temp: integer;
    i: integer;
begin
    if n <= 1 then
        return n;
    end;
    a := 0;
    b := 1;
    for i := 2 to n do
        temp := b;
        b := a + b;
        a := temp;
    end;
    return b;
end;

var
    i: integer;
begin
    for i := 0 to 20 do
        writeln(i, ": ", fibonacci(i));
    end;
end.