program flux;

const   eps=0.00001;
var     q,h:text;
        bufin,bufout:array[1..1 shl 17] of byte;
        sol:array[1..110] of double;
        nre:array[1..110] of longint;
        g:array[0..110,0..110] of double;
        a,b,c,f:array[1..5010] of longint;
        l,u,k,n,m,x,y,i,j,auxx:longint;
        rez,r,aux:double;
        ok:boolean;
        v:array of array of longint;

procedure df(nod:longint);
var       i:longint;
begin
  f[nod]:=1;
  for i:=1 to nre[nod] do
    if f[v[nod,i]]=0 then df(v[nod,i]);
end;

begin
  assign(q,'flux.in'); reset(q);
  assign(h,'flux.out'); rewrite(h);
  readln(q,n,m);
  setlength(v,n+1,1);
  for i:=1 to m do
    begin
      readln(q,a[i],b[i],c[i]);
      inc(nre[a[i]]);
      inc(nre[b[i]]);
      setlength(v[a[i]],nre[a[i]]+1);
      setlength(v[b[i]],nre[b[i]]+1);
      v[a[i]][nre[a[i]]]:=b[i];
      v[b[i]][nre[b[i]]]:=a[i];
    end;
  df(1);
  if f[n]=0 then
    begin
      r:=0;
      writeln(h,r:0:6);
      close(q);
      close(h);
      halt;
    end;
  for i:=1 to m do
    begin
      if a[i]<>1 then
        begin
          g[a[i],a[i]]:=g[a[i],a[i]]+1;
          g[a[i],b[i]]:=g[a[i],b[i]]-1;
        end;
      if b[i]<>1 then
        begin
          g[b[i],b[i]]:=g[b[i],b[i]]+1;
          g[b[i],a[i]]:=g[b[i],a[i]]-1;
        end;
    end;
  g[1,1]:=1;
  g[n,n+1]:=1;
  i:=1; j:=1;
  while (i<=n) and (j<=n) do
    begin
      ok:=true;
      for k:=i to n do
        if (g[k,j]>eps) or (g[k,j]<-eps) then
          begin
            ok:=false;
            break;
          end;
      if ok then
        begin
          inc(i); inc(j);
          continue;
        end;
      if k<>i then
        for l:=1 to n+1 do
          begin
            aux:=g[i,l];
            g[i,l]:=g[k,l];
            g[k,l]:=aux;
          end;
      for l:=j+1 to n+1 do
        g[i,l]:=g[i,l]/g[i,j];
      g[i,j]:=1;
      for u:=i+1 to n do
        begin
          if u=i then continue;
          for l:=j+1 to n+1 do
            g[u,l]:=g[u,l]-g[u,j]*g[i,l];
          g[u,j]:=0;
        end;
      inc(i); inc(j);
    end;
  for i:=n downto 0 do
    begin
      if (g[i,i]>eps) or (g[i,i]<-eps) then
        begin
          sol[i]:=g[i,n+1];
          for j:=i+1 to n do
            sol[i]:=sol[i]-g[i,j]*sol[j];
        end;
    end;
  for i:=1 to m do
    begin
      if sol[a[i]]<sol[b[i]] then
        aux:=a[i]; a[i]:=b[i]; b[i]:=auxx;
      if i=1 then rez:=c[i]/(sol[a[i]]-sol[b[i]])
      else
        if rez>c[i]/(sol[a[i]]-sol[b[i]]) then rez:=c[i]/(sol[a[i]]-sol[b[i]]);
    end;
  writeln(h,rez:0:6);
  close(q); close(h);
end.