program hurdles;
type
fxz=array[1..300,1..300] of longint;
var
f1,f2:text;
i,j,k,p,ls,x,y,n,m,t:longint;
map,max:fxz;
begin assign(f1,'hurdles.in');
      assign(f2,'hurdles.out');
      reset(f1);rewrite(f2);
      readln(f1,n,m,t);
      for i:=1to n do for j:=1to n do begin map[i,j]:=-1;max[i,j]:=-1;end;
      for i:=1to m do begin readln(f1,x,y,ls);
                            map[x,y]:=ls;
           end;
       for k:=1 to n do
       for i:=1 to n do
       for j:=1 to n do
       if (map[i,k]<>-1)and(map[k,j]<>-1)then
       if ((map[i,k]<map[i,j])and(map[k,j]<map[i,j]))or(map[i,j]=-1) then begin map[i,j]:=map[i,k];
                                                         if map[k,j]>map[i,j] then map[i,j]:=map[k,j];
         end;
      for i:=1 to t do  begin readln(f1,x,y);writeln(f2,map[x,y]);end;
      close(f1);close(f2);
end.