/* -*- coding: utf-8 -*-
 *
 * 1301.cc:  No.1301 Strange Graph Shortest Path - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MAX_M = 100000;
const long long LINF = 1LL << 62;

/* typedef */

typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,int> pli;
typedef vector<pii> vpii;

/* global variables */

int cs[MAX_M], ds[MAX_M], wis[MAX_M];
vpii nbrs[MAX_N];
ll dists[MAX_N];
pii ps[MAX_N];

/* subroutines */

ll dijkstra(int n, int st, int gl) {
  fill(dists, dists + n, LINF);
  dists[st] = 0, ps[0] = pii(-1, -1);

  priority_queue<pli> q;
  q.push(pli(0, st));

  while (! q.empty()) {
    pli u = q.top(); q.pop();
    ll ud = -u.first;
    int ui = u.second;
    if (dists[ui] != ud) continue;
    if (ui == gl) break;

    vpii &nbru = nbrs[ui];
    for (vpii::iterator vit = nbru.begin(); vit != nbru.end(); vit++) {
      int vi = vit->first, ei = vit->second;
      ll vd = ud + wis[ei];
      if (dists[vi] > vd) {
	dists[vi] = vd, ps[vi] = pii(ui, ei);
	q.push(pli(-vd, vi));
      }
    }
  }

  return dists[gl];
}

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  for (int i = 0; i < m; i++) {
    int u, v;
    scanf("%d%d%d%d", &u, &v, cs + i, ds + i);
    u--, v--;
    nbrs[u].push_back(pii(v, i));
    nbrs[v].push_back(pii(u, i));
  }
  copy(cs, cs + m, wis);

  ll d0 = dijkstra(n, 0, n - 1);
  //printf("d0=%lld\n", d0);

  for (int u = n - 1; u > 0;) {
    pli p = ps[u];
    wis[p.second] = ds[p.second];
    u = p.first;
  }

  ll d1 = dijkstra(n, n - 1, 0);

  printf("%lld\n", d0 + d1);
  return 0;
}