My program:

Program t1162;{$N+}

Const MaxM=100;
      Eps=1E-15;

Type Point=record
      S1,S2  :integer;
      RS1S2  :extended;
      CS1S2  :extended;
      RS2S1  :extended;
      CS2S1  :extended;
     end;

Var  N,M,S,i,j    :integer;
     V,CurV       :extended;
     CurS,step    :integer;
     P            :array[1..MaxM]of Point;

Procedure Rec;
var i     :integer;
    predv :extended;
 begin
  step:=step+1;
  if CurS=S then
   if CurV-V>Eps then begin
    Writeln('YES');
    Halt(0);
   end;
  if step>15000 then exit;
  predv:=curv;
  for i:=1 to m do
   if p[i].s1=curs then
    if curv>p[i].cs1s2 then begin
     curs:=p[i].s2;
     curv:=(curv-p[i].cs1s2)*p[i].rs1s2;
     rec;
     curv:=predv;
     curs:=p[i].s1;
    end;
  for i:=1 to m do
   if p[i].s2=curs then
    if curv>p[i].cs2s1 then begin
     curs:=p[i].s1;
     curv:=(curv-p[i].cs2s1)*p[i].rs2s1;
     rec;
     curv:=predv;
     curs:=p[i].s2;
    end;
  step:=step-1;
 end;

begin
 Read(N,M,S,V);
 for i:=1 to M do
  read(P[i].S1,P[i].S2,P[i].rS1S2,P[i].cS1S2,P[i].rS2S1,P[i].cS2S1);
 CurV:=V;
 CurS:=S;
 step:=0;
 Rec;
 Writeln('NO');
end.

Well,

firstly, it may take more than 15000 steps before a correct solution
is found.  15000 is way too little actually...

secondly, isn't your solution kind of slow?  There's a polynomial
time algorithm to solve it.

>