my code:

Program t1133;

Type Fib=record i,Fi :longint end;

Var a,b,c,p   :fib;
    i,j,n     :longint;
    l1,l2     :longint;
    n1,n2,cur :longint;
    p3,p2,p1  :longint;

begin
read(a.i,a.fi);
read(b.i,b.fi);
read(n);
if a.i<b.i then begin
 c:=a;
 a:=b;
 b:=c;
end;
l1:=1;
l2:=1;
if a.i-b.i>1 then
 for i:=a.i-2 downto b.i+1 do begin
  n1:=l1+l2;
  n2:=l1;
  l1:=n1;
  l2:=n2;
 end;
if a.i-b.i>1 then begin
 p.i:=b.i+1;
 p.fi:=(a.fi-l2*b.fi) div l1;
end else p:=a;
if p.i=n then cur:=p.fi else
if b.i=n then cur:=b.fi else
if a.i=n then cur:=a.fi else
if p.i<n then begin
 p1:=b.fi;
 p2:=p.fi;
 for i:=p.i+1 to n do begin
  p3:=p2+p1;
  l1:=p2;
  p2:=p3;
  p1:=l1;
 end;
 cur:=p3;
end else
if b.i>n then begin
 p3:=p.fi;
 p2:=b.fi;
 for i:=b.i-1 downto n do begin
  p1:=p3-p2;
  l1:=p2;
  p2:=p1;
  p3:=l1;
 end;
 cur:=p1;
end;
writeln(cur);
end.

[code deleted]

Edited by moderator 20.11.2019 23:18