#include <iostream>
#include <algorithm>
#include <stdlib.h>
#include <math.h>
#include <string>
#include <string.h>
#include <stdio.h>
#include <queue>


using namespace std;
const int maxn = 1e5;
typedef long long int LL;
const LL INF = 0x3f3f3f3f3f3f3f3f;
struct node
{
int next;
int value;
LL weight;
LL c;
}edge[maxn * 2 + 5];
int head[maxn * 2 + 5];
int tot;
int vis[maxn + 5];
LL d[maxn * 2 + 5];
int n, m;
void add(int x, int y, int w, int c)
{
edge[tot].value = y;
edge[tot].weight = w;
edge[tot].c = c;
edge[tot].next = head[x];
head[x] = tot++;
}
struct Node
{
int id;
LL dis;
Node() {};
Node(int id, LL dis)
{
this->id = id;
this->dis = dis;
}
friend bool operator <(Node a, Node b)
{
return a.dis>b.dis;
}
};
LL Dijkstra()
{
priority_queue<Node> q;
for (int i = 0; i<tot; i++)
d[i] = INF;
LL ans = INF;
for (int i = head[1]; i != -1; i = edge[i].next)
{
d[i] = edge[i].weight;
q.push(Node(i, d[i]));
}
while (!q.empty())
{
Node term = q.top();
q.pop();
int p = edge[term.id].value;


if (p == n)
ans = min(ans, term.dis);
for (int i = head[p]; i != -1; i = edge[i].next)
{
if (d[i]>term.dis + edge[i].weight + abs(edge[i].c - edge[term.id].c))
{
d[i] = term.dis + edge[i].weight + abs(edge[i].c - edge[term.id].c);
q.push(Node(i, d[i]));
}


}


}
return ans;
}
int main()
{
while (scanf("%d%d", &n, &m) != EOF)
{
int x, y, w, c;
memset(head, -1, sizeof(head));
tot = 0;
for (int i = 1; i <= m; i++)
{
scanf("%d%d%d%d", &x, &y, &c, &w);
add(x, y, w, c);
add(y, x, w, c);
}


printf("%lld\n", Dijkstra());
}
return 0;
}