公共汽车从始发站(称为第1站)开出,在始发站上车的人数为a,然后到达第2站,在第2站有人上、下车,但上、下车

var
a,m,n,x,i,k,aa,xx,l,aaa,xxx:longint;
s:real;

function fa(x:longint):longint;
begin
if x=2 then exit(1)
else if x=1 then exit(1)
else fa:=fa(x-1)+fa(x-2);
end;

begin
assign(input,'railway.in');
reset(input);
assign(output,'railway.out');
rewrite(output);
read(a,n,m,x);
aa:=2;
xx:=0;
for i:=4 to n-1 do
begin
aa:=aa+fa(i-2)-fa(i-3);
xx:=xx+fa(i-1)-fa(i-2);
if i=x then
begin
aaa:=aa;
xxx:=xx;
end;
end;
s:=(m-aa*a)/xx;
if s-trunc(s)<>0 then writeln('No answer.')
else begin
if x=1 then writeln(a)
else if x=2 then writeln(a)
else if x=3 then writeln(2*a)
else begin
l:=trunc(s);
writeln(aaa*a+xxx*l);
end;
end;
close(input);
close(output);
end.

题目不完整

要求什么语言?