#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;
const int inf = 1e9;
int n, m, can_to1[N], can_toN[N], can_from1[N], can_fromN[N], used[N], cnt[N][N], mn[N][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] && cnt[v][to] > 0) {
if (check(to, goal)) return true;
}
}
return false;
}
void solve() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
mn[i][j] = inf;
}
}
vector <pair<int,pair<int,int>>> save;
vector <pair<int,int>> save2;
for (int i = 1; i <= m; i++) {
int u, v, c, d;
cin >> u >> v >> c >> d;
cnt[u][v]++;
if (cnt[u][v] == 1) save2.push_back(mp(u, v));
mn[u][v] = min(mn[u][v], 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;
}
for (int i = 1; i <= n; i++) {
used[i] = 0;
}
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;
}
for (int i = 1; i <= n; i++) {
g[i].clear();
}
for (auto to : save) {
g[to.se.fi].push_back(to.se.se);
}
int res = inf;
for (auto to : save2) {
int u = to.fi, v = to.se;
int d = mn[u][v];
for (int j = 1; j <= n; j++) {
used[j] = 0;
}
g[v].push_back(u);
cnt[u][v]--;
cnt[v][u]++;
int Ok1 = check(1, n);
for (int j = 1; j <= n; j++) {
used[j] = 0;
}
int Ok2 = check(n, 1);
g[v].pop_back();
cnt[u][v]++;
cnt[v][u]--;
if (Ok1 && Ok2) {
res = min(res, d);
}
}
if (res == inf) cout << -1;
else cout << res;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while (tt--) {
solve();
// cout << '\n';
}
}
