#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000;
int main(){
  int N, M;
  cin >> N >> M;
  vector<vector<tuple<int, int, int>>> E(N);
  for (int i = 0; i < M; i++){
    int u, v, c, d;
    cin >> u >> v >> c >> d;
    u--;
    v--;
    E[u].push_back(make_tuple(v, c, d));
    E[v].push_back(make_tuple(u, c, d));
  }
  vector<long long> d1(N, INF);
  priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq1;
  pq1.push(make_pair(0, 0));
  while (!pq1.empty()){
    long long dd = pq1.top().first;
    int v = pq1.top().second;
    pq1.pop();
    if (d1[v] > dd){
      d1[v] = dd;
      for (auto edge : E[v]){
        int w = get<0>(edge);
        if (d1[w] > dd + get<1>(edge)){
          pq1.push(make_pair(dd + get<1>(edge), w));
        }
      }
    }
  }
  vector<int> pr(N, -1);
  int t = N - 1;
  while (t > 0){
    for (auto edge : E[t]){
      int w = get<0>(edge);
      if (d1[w] == d1[t] - get<1>(edge)){
        pr[t] = w;
      }
    }
    t = pr[t];
  }
  vector<vector<pair<long long, int>>> E2(N);
  for (int i = 0; i < N; i++){
    for (auto edge : E[i]){
      int w = get<0>(edge);
      if (pr[i] != w && pr[w] != i){
        E2[i].push_back(make_pair(w, get<1>(edge)));
      } else if (i == pr[w]){
        E2[i].push_back(make_pair(w, get<2>(edge)));
      } else {
        E2[i].push_back(make_pair(w, -get<1>(edge)));
      }
    }
  }
  vector<long long> d2(N, INF);
  priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq2;
  pq2.push(make_pair(0, 0));
  while (!pq2.empty()){
    long long dd = pq2.top().first;
    int v = pq2.top().second;
    pq2.pop();
    if (d2[v] > dd){
      d2[v] = dd;
      for (auto edge : E2[v]){
        int w = edge.first;
        if (d2[w] > dd + edge.second){
          pq2.push(make_pair(dd + edge.second, w));
        }
      }
    }
  }
  cout << d1[N - 1] + d2[N - 1] << endl;
}