const nmax=350;
      inf=1000*12000+1;

type ref=^nod;
     nod=record
         vf,c:integer;
         urm:ref;
         end;
     coada=^dub;
     dub=record
         x:integer;
         urm:coada;
         end;

var c,f:array[1..nmax,1..nmax] of integer;
    t:Array[1..nmax] of integer;
    g:Array[1..nmax] of ref;
    d:array[1..nmax] of longint;
    n,m,sursa,dest,nrh:integer;
    incoada:array[1..nmax] of boolean;
    buf:array[1..300000] of char;

function dijkstra:byte;
var i:integer;
    q,u,aux:coada;
    k:ref;
begin
for i:=1 to n do
 d[i]:=inf;
d[sursa]:=0;
fillchar(incoada,sizeof(incoada),false);
new(q);q^.x:=sursa; incoada[sursa]:=true;
u:=q;
while (q<>nil) do
 begin
 k:=g[q^.x];
 while k<>nil do
  begin
   if (d[k^.vf]>d[q^.x]+k^.c) and (c[q^.x,k^.vf]>f[q^.x,k^.vf]) then
    begin
     d[k^.vf]:=d[q^.x]+k^.c;
     t[k^.vf]:=q^.x;
   if not incoada[k^.vf] then
    begin
     incoada[k^.vf]:=true;
     new(aux);
     aux^.x:=k^.vf;
     u^.urm:=aux;
     u:=aux;
    end;
   end;
  k:=k^.urm;
  end;
{ aux:=q^.urm;
 incoada[q^.x]:=false;
 dispose(q);
 q:=aux;}
 incoada[q^.x]:=false;
 q:=q^.urm;
 end;

if d[dest]=inf then dijkstra:=0 else dijkstra:=1;
end;


procedure flux;
var min,k:longint;
    r:int64;
begin
r:=0;
while dijkstra<>0 do
 begin
 k:=dest;min:=maxlongint;
 while t[k]<>0 do
  begin
  if c[t[k],k]-f[t[k],k]<min then min:=c[t[k],k]-f[t[k],k];
  k:=t[k];
  end;
 k:=dest;
 while t[k]<>0 do
  begin
  inc(f[t[k],k],min);
  dec(f[k,t[k]],min);
  k:=t[k];
  end;
 inc(r,min*d[dest]);
 end;

assign(output,'fmcm.out');rewrite(output);
writeln(r);close(output);
end;

procedure adaugare(x,y,c:integer);
var p:ref;
begin
new(p);
p^.vf:=y;
p^.c:=c;
p^.urm:=g[x];
g[x]:=p;
end;

procedure citire;
var i:longword;
    x,y,c1,c2:integer;
begin
assign(input,'fmcm.in');settextbuf(input,buf);reset(input);
readln(n,m,sursa,dest);
for i:=1 to m do
 begin
 readln(x,y,c1,c2);
 c[x,y]:=c1;
 adaugare(x,y,c2);
 adaugare(y,x,-c2);
 end;
close(input);
end;

begin
citire;
flux;
end.