var a:array[0..100000,1..2] of longint;

v:array[0..100000] of longint;

s:array[0..100000] of real;

ans:boolean;

smin,smax:real;

i,j,n,m:longint;

procedure Qsort(x,y:longint);

var l,r,k:longint;

begin

l:=x; r:=y;

k:=(x+y) div 2;

repeat

while s[l]s[k] do dec(r);

if lr;

if lx then Qsort(x,r);

end;

function root(x:longint):longint;

begin

if v[x]=x then root:=x

else begin

root:=root(v[x]);

v[x]:=root;

end;

end;

procedure union(l,r:longint);

begin

l:=root(l); r:=root(r);

v[l]:=r;

end;

begin

readln(smax);

readln(n);

m:=1;

repeat

readln(a[m,1],a[m,2],s[m]);

inc(m);

until eof;

dec(m);

Qsort(1,m);

for i:=1 to n do v[i]:=i;

smin:=0;

for i:=1 to m do

if root(a)root(a) then begin

union(a,a);

smin:=smin+s[i];

end;

ans:=true;

for i:=1 to n do if v[i]v[1] then ans:=false;

if (smax>smin) and (ans) then write('Need ',smin:0:2,' miles of cable')

else write('Impossible');

end.