program hurdles(input,output);
var
 a:array[1..300,1..300]of longint;
 i,j,k,h:integer;
 n,m,t,ai,bi:integer;
 si,ei,hi:longint;

function judge(x,y:longint):longint;
begin
 if x>y then judge:=x
  else judge:=y;
end;

begin
 assign(input,'hurdles.in');
 reset(input);
 assign(output,'hurdles.out');
 rewrite(output);

 readln(n,m,t);
 for i:=1 to n do
  for j:=1 to n do
   a[i,j]:=1000001;
 for i:=1 to m do
 begin
  readln(si,ei,hi);
  a[si,ei]:=hi;
 end;

 for k:=1 to n do
  for i:=1 to n do
   for j:=1 to n do
    if (a[i,j]=1000001)or(judge(a[i,k],a[k,j])<a[i,j]) then
     a[i,j]:=judge(a[i,k],a[k,j]);

 for h:=1 to t do
 begin
  readln(ai,bi);
  if a[ai,bi]=1000001 then writeln('-1')
   else writeln(a[ai,bi]);
 end;

 close(input);
 close(output);
end.