var a, b, father : array[1..10000] of longint;

t : array[1..10000] of real;

n, e, p, i : longint;

ans, s : real;

procedure inst;

var i : longint;

begin

assign(input, 'P.in');

assign(output, 'P.out');

reset(input);

rewrite(output);

readln(s);

readln(n);

while not eof do

begin

readln(a[i], b[i], t[i]);

inc(e);

end;

if e < n - 1 then begin writeln('Impossible'); halt; end;

end;

procedure swap(var a, b : longint);

var temp : longint;

begin

temp := a;

a := b;

b := temp;

end;

procedure swap1(var a, b : real);

var temp : real;

begin

temp := a;

a := b;

b := temp;

end;

procedure qsort(l, r : longint);

var i, j : longint;

mid : real;

begin

i := l;

j := r;

mid := t[((i + j) div 2)];

repeat

while t[i] < mid do inc(i);

while t[j] > mid do dec(j);

if i j;

if j > l then qsort(l, j);

if r > i then qsort(i, r);

end;

function getfather(x : longint) : longint;

begin

if x = father[x] then exit(x);

father[x] := getfather(father[x]);

exit(father[x]);

end;

begin

inst;

qsort(1, e);

for i := 1 to n do

father[i] := i;

p := 1;

ans := 0;

for i := 1 to e do

begin

if getfather(a[i]) getfather(b[i])

then

begin

ans := ans + t[i];

father[getfather(b[i])] := a[i];

inc(p);

if p = n then break;

end;

end;

if ans