5 /* F_n = F_{n-1} + F_{n-2} */
7 struct f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 end;
10 if x < 0 then return -1; end; f0 := 0;
11 if x < 1 then return f0; end; f1 := 1;
12 if x < 2 then return f1; end; f2 := f0-(0-f1);
13 if x < 3 then return f2; end; f3 := f1-(0-f2);
14 if x < 4 then return f3; end; f4 := f2-(0-f3);
15 if x < 5 then return f4; end; f5 := f3-(0-f4);
16 if x < 6 then return f5; end; f6 := f4-(0-f5);
17 if x < 7 then return f6; end; f7 := f5-(0-f6);
18 if x < 8 then return f7; end; f8 := f6-(0-f7);
19 if x < 9 then return f8; end; f9 := f7-(0-f8);