procedure init;
var i,stv,edv:integer;
    wei:longint;
begin
fillchar(q,sizeof(q),0);
fillchar(flag,sizeof(flag),false);
fillchar(dist,sizeof(dist),127);
readln(n,e);
for i:=1 to n do
  begin
  new(p);
  head[i]:=p;
  adj[i]:=p;
  end;
for i:=1 to e do
  begin
  readln(stv,edv,wei);
  adj[stv]^.endv:=edv;
  adj[stv]^.w:=wei;
  new(p);
  adj[stv]^.next:=p;
  adj[stv]:=p;
  /////symmetry/////
  adj[edv]^.endv:=stv;
  adj[edv]^.w:=wei;
  new(p);
  adj[edv]^.next:=p;
  adj[edv]:=p
  end;
for i:=1 to n do
  adj[i]^.next:=null;
start:=1;over:=n;
end;

procedure spfa(s:longint);
var dady:integer;
begin
flag[s]:=true;q[1]:=s;dist[s]:=0;
open:=1;closed:=1;
while open<=closed do
  begin
  dady:=q[open];
  p:=head[dady];
  while (p<>nil) do
     begin
     if dist[p^.endv] > dist[dady]+p^.w
     then begin
          dist[p^.endv] := dist[dady]+p^.w;
          if not flag[p^.endv]
          then begin
               inc(closed);
               q[closed]:=p^.endv;
               flag[p^.endv]:=true;
               end;
          end;
     p:=p^.next;
     end;

  flag[dady]:=false;
  inc(open);
  end;
end;

begin
init;
null:=nil;
spfa(start);
writeln(dist[over]);
readln;readln;
end.