program hole;
var
  table:array [1..150,1..150] of longint;
  flag:array [1..150] of boolean;
  way:array [1..150] of integer;
  sum,tmp:int64;
  n,m,a,b,d,i,j:word;
  t:extended;
procedure prim(root,left:integer;s:int64);
var i,j:integer;
begin
  flag[root]:=true;way[m-left]:=root;
  if left<>0 then begin
    for i:=1 to n do if (table[root,i]<>-1) and (flag[i]=false) then begin
      tmp:=s;
      for j:=1 to m-left do if table[way[j],i]=-1 then table[way[j],i]:=table[way[j],way[m-left]]+table[root,i];
      for j:=1 to m-left do tmp:=tmp+table[way[j],i];
      prim(i,left-1,tmp);
    end;
  end
  else if s<sum then if s/(m*(m-1)/2)<t then t:=s/(m*(m-1)/2);
end;
begin
  fillchar (table,sizeof(table),$FF);
  fillchar (flag,sizeof(flag),0);
  assign (input,'hole.in');
  reset (input);
  readln (n,m);
  for i:=1 to m do begin
    readln (a,b,d);
    table[a,b]:=d;
    table[b,a]:=d;
  end;
  t:=maxlongint;sum:=maxlongint;
  for i:=1 to n do prim(i,m-1,0);
  close (input);
  assign (output,'hole.out');
  rewrite (output);
  writeln (t:0:2);
  close (output);
end.