//ALL IN
#include<bits/stdc++.h>
using namespace std;
using ll=long long;
#define int long long
#define double long double
const int N=3e5+7;
const int inf=4e18;
vector<pair<int,int>>g[N];
int n,m;
int vis[N][2];
void dfs(int x,int fa,int used,int one,int two){
    // cout<<"?"<<x<<" "<<fa<<" "<<used<<'\n';
    vis[x][used]=1;
    if(x==n){
        return;
    }
    for(auto [y,w]:g[x]){
        if(y==fa)continue;
        if(w<=two){
            if(!vis[y][0])
                dfs(y,x,0,one,two);
        }else if(w<=one){
            if(used==1)continue;
            if(!vis[y][1])
                dfs(y,x,1,one,two);
        }
    }
}
bool check(int one ,int two){
    for(int i=1;i<=n;i++)vis[i][0]=vis[i][1]=0;
    //判断最大是one 次大是two能不能使得1去往n
    dfs(1,0,0,one,two);
    if(vis[n][0]==1 or vis[n][1]==1)return 1;
    return 0;
}
void solve(){
    cin>>n>>m;
    int mx=0;
    for(int i=1;i<=m;i++){
        int u,v,w;cin>>u>>v>>w;
        g[u].push_back({v,w});
        g[v].push_back({u,w});
        mx=max(mx,w);
    }
    int ans=inf;
    int l=0,r=mx+1;
    while(l+1!=r){
        int mid=l+r>>1;
        int ll=-1,rr=mid+1;
        int flag=0;
        while(ll+1!=rr){
            // cout<<"?"<<l<<" "<<r<<" "<<ll<<" "<<rr<<'\n';
            int midmid=ll+rr>>1;
            // cout<<mid<<" "<<midmid<<'\n';
            // cout<<check(mid,midmid)<<"\n\n";
            if(check(mid,midmid)){
                ans=min(ans,mid+midmid);
                rr=midmid;
                flag=1;
            }else{
                ll=midmid;
            }
        }
        if(flag)r=mid;
        else l=mid;
    }
    cout<<ans<<'\n';
}

signed main(){
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    int _=1;
    // cin>>_;
    while(_--)solve();
}