#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL_
void debug_out() {cerr << endl;}
template<typename Head,typename... Tail> void debug_out(Head H,Tail... T){cerr << ' ' << H; debug_out(T...);}
#define debug(...) cerr << 'L' << __LINE__ << " [" << #__VA_ARGS__ << "]:",debug_out(__VA_ARGS__)
#define dump(x) cerr << 'L' << __LINE__ << " " << #x << " = " << (x) << endl;
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
#define rep(i,n) for (int i = 0; i < (int)(n); i ++)
#define irep(i,n) for (int i = (int)(n) - 1;i >= 0;--i)
using ll = long long;
using PL = pair<ll,ll>;
using P = pair<int,int>;
constexpr int INF = 1000000000;
constexpr long long HINF = 100000'00000'00000;
constexpr long long MOD = 1000000007;// = 998244353;
constexpr double EPS = 1e-4;
constexpr double PI = 3.14159265358979;

#pragma region Macros
template<typename T1,typename T2> ostream &operator<<(ostream &os,const pair<T1,T2> &p) {
    os << '(' << p.first << ',' << p.second << ')'; return os;
}
template<typename T> ostream &operator<<(ostream &os,const vector<T> &v) {
    os << '[';
    for (auto &e:v) {os << e << ',';}
    os << ']'; return os;
}
// grid searh
const int dy[8] = {-1,0,1,0,-1,-1,1,1};
const int dx[8] = {0,1,0,-1,-1,1,-1,1};
bool IN(int y,int x,int H,int W) {return (0 <= y)&&(y < H)&&(0 <= x)&&(x < W);}
#pragma endregion


int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);

    int N,M; cin >> N >> M;
    vector<vector<P>> G(N);
    vector<int> C(M),D(M),used(M,-1);
    rep(i,M) {
        int a,b,c,d; cin >> a >> b >> c >> d;
        --a; --b;
        G[a].emplace_back(b,i);
        G[b].emplace_back(a,i);
        C[i] = c;
        D[i] = d;
    } 


    vector<ll> dist(N,HINF);
    vector<int> before(N,-1);
    dist[0] = 0;

    priority_queue<PL,vector<PL>,greater<PL>> q;
    q.push({0,0});

    while (!q.empty()) {
        PL p = q.top(); q.pop();
        ll d = p.first;
        int v = p.second;
        if (dist[v] < d) continue;
        for (PL p: G[v]) {
            int e = p.first;
            ll cost = C[p.second];
            if (dist[e] > dist[v] + cost) {
                dist[e] = dist[v] + cost;
                before[e] = v;
                q.push({dist[e],e});
            }
        }  
    }

    int v = N-1;
    while (v > 0) {
        for (P p:G[v]) {
            if (p.first == before[v]) {
                used[p.second] = 1;
                break;
            }
        }
        v = before[v];
    }

    vector<ll> dist2(N,HINF);
    dist2[N-1] = 0;

    q.push({0,N-1});

    while (!q.empty()) {
        PL p = q.top(); q.pop();
        ll d = p.first;
        int v = p.second;
        if (dist2[v] < d) continue;
        for (PL p: G[v]) {
            int e = p.first;
            ll cost;
            if (used[p.second] >= 0) cost = D[p.second];
            else cost = C[p.second];
            if (dist2[e] > dist2[v] + cost) {
                dist2[e] = dist2[v] + cost;
                q.push({dist2[e],e});
            }
        }  
    }
    cout << dist[N-1] + dist2[0] << '\n';
    return 0;
}