#include <limits>
#include <initializer_list>
#include <utility>
#include <bitset>
#include <tuple>
#include <type_traits>
#include <functional>
#include <string>
#include <array>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <iterator>
#include <algorithm>
#include <complex>
#include <random>
#include <numeric>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <regex>
#include <cassert>
#include <cstddef>
#include <variant>

#define endl codeforces

#define ALL(v) std::begin(v), std::end(v)
#define ALLR(v) std::rbegin(v), std::rend(v)

using ll = std::int64_t;
using ull = std::uint64_t;
using pii = std::pair<int, int>;
using tii = std::tuple<int, int, int>;
using pll = std::pair<ll, ll>;
using tll = std::tuple<ll, ll, ll>;
using size_type = ssize_t;
template <typename T> using vec = std::vector<T>;
template <typename T> using vvec = vec<vec<T>>;

template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }

template <typename T, std::size_t Head, std::size_t... Tail> 
struct multi_dim_array { using type = std::array<typename multi_dim_array<T, Tail...>::type, Head>; };

template <typename T, std::size_t Head> 
struct multi_dim_array<T, Head> { using type = std::array<T, Head>; };

template <typename T, std::size_t... Args> using mdarray = typename multi_dim_array<T, Args...>::type;

template <typename T, typename F, typename... Args> 
void fill_seq(T &t, F f, Args... args) { 
    if constexpr (std::is_invocable<F, Args...>::value) { 
        t = f(args...); 
    } else { 
        for (size_type i = 0; i < t.size(); i++) fill_seq(t[i], f, args..., i); 
    } 
}

template <typename T> vec<T> make_v(size_type sz) { return vec<T>(sz); }

template <typename T, typename... Tail> 
auto make_v(size_type hs, Tail&&... ts) { 
    auto v = std::move(make_v<T>(std::forward<Tail>(ts)...)); 
    return vec<decltype(v)>(hs, v); 
}

namespace init__ { 
struct InitIO { 
    InitIO() { 
        std::cin.tie(nullptr); 
        std::ios_base::sync_with_stdio(false); 
        std::cout << std::fixed << std::setprecision(30); 
    } 
} init_io; 
}

template <typename T>
T ceil_pow2(T bound) {
    T ret = 1;
    while (ret < bound) ret *= 2;
    return ret;
}

template <typename T>
T ceil_div(T a, T b) { return a / b + !!(a % b); }


int main() {
    ll n, m;
    std::cin >> n >> m;
    using raw_edge = std::tuple<ll, ll, ll, ll>;
    vec<raw_edge> edges(m);
    for (auto &[ u, v, c, d ] : edges) {
        std::cin >> u >> v >> c >> d;
        u--; v--;
    }

    vec<ll> cost1(m), cost2(m);
    vvec<pll> g(n);
    for (ll i = 0; i < m; i++) {
        auto [ u, v, c , d ] = edges[i];
        cost1[i] = c;
        cost2[i] = d;
        g[u].emplace_back(v, i);
        g[v].emplace_back(u, i);
    }

    constexpr ll inf = 5e15;

    vec<bool> used(m, false);
    vec<ll> prev(m, -inf);

    auto get_adj = [&](ll u, pll e) {
        auto [ a, b ] = e;
        if (u == a) return b;
        else return a;
    };

    auto get_cost = [&](ll idx) {
        if (used[idx]) return cost2[idx];
        return cost1[idx];
    };

    auto dijk = [&] {
        std::priority_queue<tll, vec<tll>, std::greater<tll>> pq;
        vec<ll> dists(n, inf);
        dists[0] = 0;
        pq.emplace(0, 0, -1);
        while (pq.size()) {
            auto [ d, cur, eidx ] = pq.top();
            pq.pop();
            if (dists[cur] < d) continue;
            prev[cur] = eidx;
            for (auto [ nxt, i ] : g[cur]) {
                auto nd = d + get_cost(i);
                if (dists[nxt] <= nd) continue;
                dists[nxt] = nd;
                pq.emplace(nd, nxt, i);
            }
        }
        return dists;
    };

    auto d1 = dijk();
    ll cur = n - 1;
    while (cur) {
        auto idx = prev[cur];
        used[idx] = true;
        auto [ u, v, c, d ] = edges[idx];
        auto p = get_adj(cur, pll(u, v));
        cur = p;
    }
    auto d2 = dijk();
    std::cout << d1.back() + d2.back() << "\n";
    return 0;
}