#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
template<int mod>istream &operator>>(istream &is,static_modint<mod> &a){long long b;is>>b;a=b;return is;}
istream &operator>>(istream &is,modint &a){long long b;cin>>b;a=b;return is;}
#endif
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) static_cast<void>(0)
#define debugg(...) static_cast<void>(0)
#define esper(...) static_cast<void>(0)
template<typename T1,typename T2>ostream &operator<<(ostream &os,const pair<T1,T2>&p){os<<p.first<<' '<<p.second;return os;}
#endif
using ll=long long;
using ull=unsigned long long;
using P=pair<ll,ll>;
template<typename T>using minque=priority_queue<T,vector<T>,greater<T>>;
template<typename T>bool chmax(T &a,const T &b){return (a<b?(a=b,true):false);}
template<typename T>bool chmin(T &a,const T &b){return (a>b?(a=b,true):false);}
template<typename T1,typename T2>istream &operator>>(istream &is,pair<T1,T2>&p){is>>p.first>>p.second;return is;}
template<typename T>istream &operator>>(istream &is,vector<T> &a){for(auto &i:a)is>>i;return is;}
template<typename T1,typename T2>void operator++(pair<T1,T2>&a,int n){a.first++,a.second++;}
template<typename T1,typename T2>void operator--(pair<T1,T2>&a,int n){a.first--,a.second--;}
template<typename T>void operator++(vector<T>&a,int n){for(auto &i:a)i++;}
template<typename T>void operator--(vector<T>&a,int n){for(auto &i:a)i--;}
#define reps(i,a,n) for(int i=(a);i<(n);i++)
#define rep(i,n) reps(i,0,n)
#define all(x) x.begin(),x.end()
#define pcnt(x) __builtin_popcountll(x)
#define fin(x) return cout<<x<<'\n',static_cast<void>(0)
ll myceil(ll a,ll b){return (a+b-1)/b;}
template<typename T,size_t n,size_t id=0>
auto vec(const int (&d)[n],const T &init=T()){
  if constexpr (id<n)return vector(d[id],vec<T,n,id+1>(d,init));
  else return init;
}
void SOLVE();
int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout<<fixed<<setprecision(16);
  #ifdef LOCAL
  clock_t start=clock();
  #endif
  int testcase=1;
  //cin>>testcase;
  for(int i=0;i<testcase;i++){
    SOLVE();
  }
  #ifdef LOCAL
  cerr<<"time:";
  cerr<<(clock()-start)/1000;
  cerr<<"ms\n";
  #endif
}
template<typename T>
struct convex_hull_trick{
private:
  struct node{
    node *left,*right;
    static const T inf=numeric_limits<T>::max();
    T a,b;
    node():node(0,inf){}
    node(const T a,const T b):left(nullptr),right(nullptr),a(a),b(b){}
    T f(const T x)const{return a*x+b;}
  };
  static void swap(node *x,node *y){
    std::swap(x->a,y->a),std::swap(x->b,y->b);
  }
  void add(node *cu,node *nw,T l,T r){
    while(true){
      if(nw->f(l)<cu->f(l))swap(cu,nw);
      if(cu->f(r-1)<=nw->f(r-1))return;
      T mid=(l+r)/2;
      if(cu->f(mid)<=nw->f(mid)){
        if(!cu->right){
          cu->right=new node(*nw);
          return;
        }
        else{
          cu=cu->right,l=mid;
        }
      }
      else{
        swap(cu,nw);
        if(!cu->left){
          cu->left=new node(*nw);
          return;
        }
        else{
          cu=cu->left,r=mid;
        }
      }
    }
  }
  T query(node *cu,T k,T l,T r)const{
    T ans=numeric_limits<T>::max();
    while(cu){
      chmin(ans,cu->f(k));
      T mid=(l+r)/2;
      if(k<mid){
        cu=cu->left,r=mid;
      }
      else{
        cu=cu->right,l=mid;
      }
    }
    return ans;
  }
  void clear(node *cu){
    if(cu->left)clear(cu->left);
    if(cu->right)clear(cu->right);
    delete cu;
  }
  const T l,r;
  node *root;
public:
  convex_hull_trick(const T l,const T r):l(l),r(r),root(new node()){
    assert(l<r);
  }
  //y=a*x+b
  void add(const T a,const T b){
    node nw(a,b);
    return add(root,&nw,l,r);
  }
  T query(const T k)const{
    return query(root,k,l,r);
  }
};
void SOLVE(){
  int n,m;
  cin>>n>>m;
  vector<ll>w(n);
  cin>>w;
  vector<vector<pair<int,ll>>>to(n);
  rep(i,m){
    int u,v,t;
    cin>>u>>v>>t;
    u--,v--;
    to[u].push_back({v,t});
    to[v].push_back({u,t});
  }
  auto dij=[&](int st)->vector<ll> {
    vector<ll>dst(n,1e18);
    dst[st]=0;
    minque<pair<ll,int>>que;
    que.push({0,st});
    while(!que.empty()){
      auto [d,x]=que.top();que.pop();
      if(dst[x]!=d)continue;
      for(auto i:to[x])if(chmin(dst[i.first],d+i.second))que.push({dst[i.first],i.first});
    }
    return dst;
  };
  vector<ll>l=dij(0),r=dij(n-1);
  ll ans=l[n-1];
  convex_hull_trick<ll>cht(-1e10,1e10);
  rep(i,n)cht.add(w[i],l[i]);
  rep(i,n)chmin(ans,cht.query(w[i])+r[i]);
  cout<<ans<<endl;
}