#pragma GCC optimize("Ofast") #include #define rep(i,n) for(int i=0;i>x[i]; #define ft first #define sc second #define pb push_back #define lb lower_bound #define ub upper_bound #define all(v) (v).begin(),(v).end() #define LB(a,x) lb(all(a),x)-a.begin() #define UB(a,x) ub(all(a),x)-a.begin() #define mod 1000000007 //#define mod 998244353 #define FS fixed< using V=vector; using P=pair; typedef unsigned long long ull; typedef long double ldouble; template inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; } template inline void out(T a){ cout << a << '\n'; } void YN(bool ok){if(ok) cout << "Yes" << endl; else cout << "No" << endl;} //void YN(bool ok){if(ok) cout << "YES" << endl; else cout << "NO" << endl;} const ll INF=1e18; const int mx=200005; struct edge{ ll to,cost; }; int main(){ //オーバーフローは大丈夫ですか?? cin.tie(0);ios::sync_with_stdio(false); int n,m; cin>>n>>m; V> G(n); rep(i,m){ ll s,t,d; cin>>s>>t>>d; s--;t--; G[s].pb({t,d}); G[t].pb({s,d}); } ll L=0,R=1000000000+1; ll ans=INF; while(R-L>1){ ll mid=(L+R)/2; V d(n,-1); queue que; que.push(0); d[0]=0; while(que.size()){ int v=que.front(); que.pop(); for(edge e:G[v]){ int nv=e.to; if(d[nv]!=-1) continue; if(mid<=e.cost){ d[nv]=d[v]+1; que.push(nv); } } } if(d[n-1]>=0){ L=mid; ans=d[n-1]; }else{ R=mid; } } cout<