#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define mp make_pair
#define Sz(x) (int)x.size()
using namespace std;
const int N = 205;
int n, m, can_to1[N], can_toN[N], can_from1[N], can_fromN[N], used[N];
vector <int> g[N];
void dfs(int v, int tp) {
used[v] = 1;
if (!tp) can_from1[v] = 1;
else can_fromN[v] = 1;
for (auto to : g[v]) {
if (!used[to]) {
dfs(to, tp);
}
}
}
void dfs2(int v, int tp) {
used[v] = 1;
if (!tp) can_to1[v] = 1;
else can_toN[v] = 1;
for (auto to : g[v]) {
if (!used[to]) {
dfs2(to, tp);
}
}
}
bool check(int v, int goal) {
used[v] = 1;
if (v == goal) return true;
for (auto to : g[v]) {
if (!used[to]) {
if (check(to, goal)) return true;
}
}
return false;
}
void solve() {
cin >> n >> m;
vector <pair<int,pair<int,int>>> save;
for (int i = 1; i <= m; i++) {
int u, v, c, d;
cin >> u >> v >> c >> d;
g[u].push_back(v);
save.push_back(mp(d, mp(u, v)));
}
int ok1 = check(1, n);
for (int i = 1; i <= n; i++) {
used[i] = 0;
}
int ok2 = check(n, 1);
if (ok1 && ok2) {
cout << 0;
return;
}
sort(save.begin(), save.end());
dfs(1, 0);
for (int i = 1; i <= n; i++) {
used[i] = 0;
}
dfs(n, 1);
for (int i = 1; i <= n; i++) {
used[i] = 0;
g[i].clear();
}
for (auto to : save) {
int u = to.se.fi, v = to.se.se;
g[v].push_back(u);
}
dfs2(1, 0);
for (int i = 1; i <= n; i++) {
used[i] = 0;
}
dfs2(n, 1);
if (!ok1 && !ok2) {
for (auto to : save) {
int d = to.fi, u = to.se.fi, v = to.se.se;
if (can_from1[v] && can_fromN[v] && can_to1[u] && can_toN[u]) {
cout << d;
return;
}
}
cout << -1;
return;
}
int s = 1, f = n;
if (ok2) swap(s, f);
for (int i = 0; i < Sz(save); i++) {
pair <int,pair<int,int>> to = save[i];
int d = to.fi, u = to.se.fi, v = to.se.se;
for (int j = 1; j <= n; j++) {
g[j].clear();
used[j] = 0;
}
g[v].push_back(u);
for (int j = 0; j < Sz(save); j++) {
if (j == i) continue;
g[save[j].se.fi].push_back(save[j].se.se);
}
int Ok1 = check(s, f);
for (int j = 1; j <= n; j++) {
used[j] = 0;
}
int Ok2 = check(f, s);
if (Ok1 && Ok2) {
cout << d;
return;
}
}
cout << -1;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while (tt--) {
solve();
// cout << '\n';
}
}
