#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) templateistream&operator >>(istream&is,vector&vec){for(T&x:vec)is>>x;return is;} templateinline void out(T t){cout << t << "\n";} templateinline void out(T t,Ts... ts){cout << t << " ";out(ts...);} templateinline bool CHMIN(T&a,T b){if(a > b){a = b;return true;}return false;} templateinline 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; vector> 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); } vectorrev(N, -1); priority_queue, vector>, greater>> que; vectordist(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(N, -1); { int now = N - 1; while(preRev[now] != -1) { rev[now] = preRev[now]; now = rev[now]; } } auto preDist = dist; dist = vector(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]); }