program ex;
type
 ss=array[1..300,1..300]of longint;
var
 map:ss;
 n,m,t:longint;
procedure floyed;
 var
  i,j,k:longint;
 begin
  for k:=1 to n do
   for i:=1 to n do
    for j:=1 to n do
     if (map[i,k]>0)and(map[k,j]>0)then
      if (map[k,j]<map[i,j])and(map[i,k]<map[i,j])or(map[i,j]=0) then
       if map[i,k]>map[k,j] then map[i,j]:=map[i,k]
                            else map[i,j]:=map[k,j];
 end;
procedure init;
 var
  s,e,h:longint;
  i,j:longint;
 begin
  assign(input,'hurdles.in');
  assign(output,'hurdles.out');
  reset(input);
  rewrite(output);
  readln(n,m,t);
  for i:=1 to m do
   begin
    readln(s,e,h);
    map[s,e]:=h;
   end;
  floyed;
  for i:=1 to t do
   begin
    readln(s,e);
    if map[s,e]=0
     then writeln('-1')
     else writeln(map[s,e]);
   end;
 end;
begin
 init;
 close(input);
 close(output);
end.