#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define chmin(x,y) x = min((x),(y));
#define chmax(x,y) x = max((x),(y));
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
const int INF = 1e9;
const long long LINF = 1e17;
const int MOD = 1000000007;
//const int MOD = 998244353;
const double PI = 3.14159265358979323846;


int n = 100005;
int m;
vector<map<ll,ll>> graph(n);

using p = pair<pll,int>;
vector<ll> before(n);

vector<ll>  Dijkstra(int start){
    vector<bool> seen(n,false);
    vector<ll> shortest(n,LINF);
    priority_queue<p,vector<p>,greater<p>> pq;
    pq.push(p(pll{0,start},-1));

    while(!pq.empty()){
        ll dist = pq.top().first.first;
        int node = pq.top().first.second;
        int b = pq.top().second;
        pq.pop();
        if(seen[node]) continue;

        shortest[node] = dist;
        before[node] = b;
        seen[node] = true;

        for(auto next:graph[node]){
            int next_node = next.first;
            ll next_cost = next.second;
            if(seen[next_node]) continue;
            pq.push(p(pll{next_cost + dist,next_node},node));
        }
    }

    return shortest;
}


int main(){
    cin >> n >> m;
    map<P,ll> dist;
    rep(i,m){
        int u,v,c,d;
        cin >> u >> v >> c >> d;
        --u;--v;
        graph[u][v] = c;
        graph[v][u] = c;
        if(u>v) swap(u,v);
        dist[P(u,v)] = d;
    }

    //rep(i,n){
        //for(auto p:graph[i])
    //}

    vector<ll> res = Dijkstra(0);
    //rep(i,n) cout << res[i] << " ";
    //cout << endl;

    int now = n-1;
    while(now > 0){
        int a = now;
        int b = before[now];

        graph[a][b] = dist[P(min(a,b),max(a,b))];
        graph[b][a] = graph[a][b];

        now = b;
        //cout << now << endl;
    }
    

    vector<ll> ret = Dijkstra(n-1);
    cout << res[n-1] + ret[0] << endl;

    return 0;
}