#include "bits/stdc++.h"
using namespace std;
//#include "atcoder/all"
//using namespace atcoder;
#define int long long
#define REP(i, n) for (int i = 0; i < (int)n; ++i)
#define RREP(i, n) for (int i = (int)n - 1; i >= 0; --i)
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define RFOR(i, s, n) for (int i = (int)n - 1; i >= s; --i)
#define ALL(a) a.begin(), a.end()
#define IN(a, x, b) (a <= x && x < b)
template<class T>istream&operator >>(istream&is,vector<T>&vec){for(T&x:vec)is>>x;return is;}
template<class T>inline void out(T t){cout << t << "\n";}
template<class T,class... Ts>inline void out(T t,Ts... ts){cout << t << " ";out(ts...);}
template<class T>inline bool CHMIN(T&a,T b){if(a > b){a = b;return true;}return false;}
template<class T>inline bool CHMAX(T&a,T b){if(a < b){a = b;return true;}return false;}
constexpr int INF = 1e18;

signed main(){
	int N, M;
	cin >> N >> M;
	using T = tuple<int, int, int>;
	vector<vector<T>> g(N);
	REP(i, M) {
		int a, b, c, d;
		cin >> a >> b >> c >> d;
		--a; --b;
		g[a].emplace_back(b, c, d);
		g[b].emplace_back(a, c, d);
	}
	vector<int>rev(N, -1);
	priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> que;
	vector<int>dist(N, INF);
	dist[0] = 0;
	que.push({0, 0});
	while(que.size()) {
		auto[cost, now] = que.top();
		que.pop();
		if(dist[now] != cost) continue;
		for(auto [e, c, d]: g[now]) {
			if(CHMIN(dist[e], cost + c)) {
				que.push({dist[e], e});
				rev[e] = now;
			}
		}
	}
	auto preRev = rev;
	rev = vector<int>(N, -1);
	{
		int now = N - 1;
		while(preRev[now] != -1) {
			rev[now] = preRev[now];
			now = rev[now];
		}
	}
	auto preDist = dist;
	dist = vector<int>(N, INF);
	dist[0] = 0;
	que.push({0, 0});
	while(que.size()) {
		auto[cost, now] = que.top();
		que.pop();
		if(dist[now] != cost) continue;
		for(auto [e, c, d]: g[now]) {
			if(rev[e] == now) {
				if(CHMIN(dist[e], cost + d)) {
					que.push({dist[e], e});
				}
			} else {
				if(CHMIN(dist[e], cost + c)) {
					que.push({dist[e], e});
				}
			}
		}
	}
	out(preDist[N - 1] + dist[N - 1]);
}