#include <bits/stdc++.h>
#define int 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 = 1e18;
int n, m, used[N], comp[N];
vector <int> g[N], order;
void dfs(int v) {
used[v] = 1;
for (auto to : g[v]) {
if (!used[to])
dfs(to);
}
order.push_back(v);
}
void dfs2(int v, int ind) {
comp[v] = ind;
used[v] = 1;
for (auto to : g[v]) {
if (!used[to])
dfs2(to, ind);
}
}
void solve() {
cin >> n >> m;
vector <pair<pair<int,int>,int>> edges;
vector <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);
edges.push_back(mp(mp(u, v), d));
save.push_back(mp(u, v));
}
for (int i = 1; i <= n; i++) {
if (!used[i]) {
dfs(i);
}
}
reverse(order.begin(), order.end());
for (int i = 1; i <= n; i++) {
g[i].clear();
used[i] = 0;
}
for (auto [u, v] : save) {
g[v].push_back(u);
}
int sz = 0;
for (auto to : order) {
if (!used[to]) {
dfs2(to, ++sz);
}
}
if (comp[1] == comp[n]) {
cout << 0;
return;
}
for (int i = 1; i <= n; i++) {
g[i].clear();
used[i] = 0;
}
for (auto [u, v] : save) {
if (comp[u] != comp[v]) {
g[comp[u]].push_back(comp[v]);
}
}
int s = 1, f = n;
if (comp[s] > comp[f]) swap(s, f);
dfs(comp[s]);
if (!used[f]) {
cout << -1;
return;
}
for (int i = 1; i <= n; i++) {
used[i] = 0;
}
dfs(comp[f]);
int ans = inf;
vector <int> have;
for (auto to : edges) {
int v = to.fi.fi, u = to.fi.se, d = to.se;
if (comp[v] == comp[s] && used[comp[u]] && comp[u] != comp[f]) {
ans = min(ans, d);
}
if (comp[v] == comp[s] && comp[u] == comp[f]) {
have.push_back(d);
}
}
sort(have.begin(), have.end());
if (Sz(have) >= 2) ans = min(ans, have[0]);
if (ans == inf) cout << -1;
else cout << ans;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while (tt--) {
solve();
// cout << '\n';
}
}
