#include <bits/stdc++.h>

using namespace std;
#define fi first
#define se second
#define int long long
typedef pair<int, int> PII;
const int mod = 1e9 + 7;
const int N = 1e6 + 10;
struct node {
    int x, c, t;
};
vector<node> e[N];
int dist[N];
bool st[N];
int cc[N];

void dijkstra() {
    priority_queue<PII, vector<PII>, greater<PII> > q;
    dist[1] = 0;
    q.push({dist[1], 1});
    while (q.size()) {
        int ver = q.top().second;
        q.pop();

        if (st[ver]) continue;
        st[ver] = 1;

        for (auto &[j, c, t] : e[ver]) {
            if (ver == 1) {
                cc[1] = c;
            }
            if (dist[j] > dist[ver] + t + abs(cc[ver] - c)) {
                dist[j] = dist[ver] + t + abs(cc[ver] - c);
                cc[j] = c;
                q.push({dist[j], j});
            }
        }
    }
}

void solve() {
    int n, m;
    while (cin >> n >> m) {
        for (int i = 1; i <= n; i++) {
            e[i].clear();
            dist[i] = 1e18;
            st[i] = 0;
        }
        for (int i = 0; i < m; i++) {
            int a, b, c, t;
            cin >> a >> b >> c >> t;
            e[a].push_back({b, c, t});
            e[b].push_back({a, c, t});
        }
        dijkstra();
        cout << dist[n] << '\n';
    }
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int tma = 15;
    int _;
    _ = 1;
    // cin >> _;
    while (_--) {
        solve();
    }
}