It works like this:
f1=1*f1+0*f2;
f2=0*f1+1*f2;
f3=1*f1+1*f2;
f4=1*f1+2*f2;
f5=2*f1+3*f2;
f6=3*f1+5*f2;
...^....^
...|....These coefficients are in the array c2
...These coefficients are in the array c1

----PROG BELOW----
program ural1133;
const
  maxn=2001;
var
  c1,c2:array[1..maxn]of extended;
  x,y,n,i:integer;
  fx,fy,f1,f2:longint;
function min(a,b:integer):integer;
  begin
    if a<b then min:=a else min:=b;
  end;
function max(a,b:integer):integer;
  begin
    if a>b then max:=a else max:=b;
  end;
begin
  readln(x,fx,y,fy,n);
  i:=min(min(x,y),n);
  if i<=0 then begin
    i:=1-i;
    inc(x,i);inc(y,i);inc(n,i);
  end;

  c1[1]:=1;c2[1]:=0;
  c1[2]:=0;c2[2]:=1;
  for i:=3 to max(max(x,y),n) do begin
    c1[i]:=c1[i-2]+c1[i-1];
    c2[i]:=c2[i-2]+c2[i-1];
  end;

  f1:=round((fx*c2[y]-fy*c2[x])/(c1[x]*c2[y]-c1[y]*c2[x]));
  f2:=round((fx*c1[y]-fy*c1[x])/(c2[x]*c1[y]-c2[y]*c1[x]));
  writeln(round(c1[n]*f1+c2[n]*f2));
end.

Try this:

46 1836311903 -46 -1836311903 45

Correct answer is 1134903170, but your program outputs 1073741824.

I have the same problem. Can anybody help?

Edited by author 10.11.2007 16:27

>> writeln(round(c1[n]*f1+c2[n]*f2));
For example c1[n]*f1 may exceed extended (c1[n]*f1+c2[n]*f2 don't, but you will lost correctness), and as I understand, test from UNKNOWN LAMER (thanks!), makes it true

Edited by author 10.11.2007 16:33

that's true,thanks

i use round an correct