type ref=^nod;
nod=record
    nr:longint;
    adr:ref;
    end;
var a:array[1..100,1..100] of longint;
s:array[1..100] of 0..1;
v,sf,u2,cost,cost2:ref;
n,m,x,y,i,j,k,c:longint;
f,g:text;
ok:boolean;
begin
assign(f,'sate.in');
assign(g,'sate.out');
reset(f);rewrite(g);
readln(f,n,m,x,y);
for i:=1 to n do
    for j:=1 to n do
        if i<>j then
           a[i,j]:=-1;
for i:=1 to m do
    begin
    readln(f,j,k,c);
    a[j,k]:=c;
    a[k,j]:=c;
    end;
new(v);
v^.nr:=x;
v^.adr:=nil;
s[x]:=1;
sf:=v;
new(cost);
cost^.nr:=0;
cost^.adr:=nil;
cost2:=cost;
repeat
      for i:=1 to n do
          if (a[v^.nr,i]>0) and (s[i]=0) then
             begin
             s[i]:=1;
             new(u2);
             u2^.nr:=i;
             u2^.adr:=nil;
             sf^.adr:=u2;
             sf:=u2;
             new(u2);
             if v^.nr<i then
                u2^.nr:=cost^.nr+a[v^.nr,i]
             else
                 u2^.nr:=cost^.nr-a[v^.nr,i];
             u2^.adr:=nil;
             cost2^.adr:=u2;
             cost2:=u2;
             if i=y then
                begin
                ok:=true;
                break;
                end;
             end;
      if ok=false then
         begin
         u2:=v^.adr;
         dispose(v);
         v:=u2;
         u2:=cost^.adr;
         dispose(cost);
         cost:=u2;
         end;
until ok=true;
write(g,cost2^.nr);
close(f);close(g);
end.