program hurdles;
var
  map:array[0..301,0..301]of longint;
  i,j,k,m,n,t,a,b,c:longint;
begin
  assign(input,'hurdles.in');
  assign(output,'hurdles.out');
  reset(input); rewrite(output);
  readln(n,m,t);
  for i:=0 to 301 do  for j:=0 to 301 do map[i,j]:=-1;
  for i:=1 to m do begin
    readln(a,b,c);
    map[a,b]:=c;
  end;
  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 begin
          a:=map[i,j]; b:=map[i,k]; c:=map[k,j];
          if c>b then b:=c;
          if (a>b)or(a=-1)then map[i,j]:=b;
  end;
  for i:=1 to t do begin
    readln(a,b);
    writeln(map[a,b]);
  end;
  close(input); close(output);
END.