// Slower C++ solution:
#include<iostream>

#include<vector>

#include<queue>

#include<algorithm>

#include<cstring>

using namespace std;

const int maxn  = 1e4+10;

const int INF = 0x3f3f3f3f;

typedef pair<int,int> P;

struct edge{

	int to,dis,cost;

		

};



int d[maxn];

int value[maxn];



int N,M;



int dijkstra(vector<edge>G[])

{



	memset(d,INF,sizeof(d));

	//memset(value,INF,sizeof(value));

	priority_queue<P,vector<P>,greater<P> > que;

		

	d[1] = 0;

	value[1] = 0;

	que.push(P(d[1],1));

	

	int res = 0;

	while(!que.empty())

	{

		P p  = que.top(); que.pop();

		

		int v = p.second;

		if(d[v] < p.first)

			continue;

			

		res += value[v];

		

		for(int i = 0; i < G[v].size(); i++)

		{

			edge e = G[v][i];

			if(d[e.to] == d[v] + e.dis)

				value[e.to] = min(value[e.to],e.cost);

			if(d[e.to] > d[v] + e.dis)

			{

				d[e.to] = d[v] + e.dis;

				que.push(P(d[e.to],e.to));

				

				value[e.to] = e.cost;

			}

		}

	}

	return res;

	

}



int main()

{



	//freopen("c:\\users\\administrator\\desktop\\in.txt","r",stdin);

	while(cin >> N >> M, N||M)

	{

		

		vector<edge> G[maxn];

		for(int i =0; i < M; i++)

		{

			int u,v,d,c;

			edge e;

			cin >> u >> v >> d >> c;

			e.to= v, e.dis= d, e.cost =c;

			G[u].push_back(e);

			e.to= u;

			G[v].push_back(e);	

		}

		

		int res = dijkstra(G);

		cout << res <<endl;

	}		

} 

// Faster C++ solution for the same problem (measured speedup: 1.434291523112535x):
#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <queue>

using namespace std;



#define MAXN 20005

#define MAXE 40005

#define INF 0x3f3f3f3f



typedef int Type;



class Dijkstra

{

public:

    int head[MAXN],nxt[MAXE],cnt;

    Type d[MAXN];

    struct Edge

    {

        int v;

        Type dis;

        Type cost;

        Edge() {}

        Edge(int v,Type dis,Type cost):v(v),dis(dis),cost(cost) {}

        bool operator<(const Edge& ed) const

        {

            return dis>ed.dis;

        }

    } e[MAXE];

    bool vis[MAXN];



    //初始化，n?点数

    void init(int n)

    {

        cnt = 0;

        for(int i = 0; i<=n; i++) head[i] = -1;

    }



    inline void addEdge(int u,int v,Type dis,Type cost)

    {

        e[cnt] = Edge(v,dis,cost);

        int tmp = head[u];

        head[u] = cnt;

        nxt[cnt++] = tmp;

    }



    void dijkstra(int s,int t,int n)

    {

        for(int i = 0; i<=n; i++) d[i] = INF,vis[i] = false;

        d[s] = 0;

        priority_queue<Edge> q;

        q.push(Edge(s,0,0));

        while(!q.empty())

        {

            Edge ed = q.top();

            q.pop();

            vis[ed.v] = true;

            for(int i = head[ed.v]; ~i; i = nxt[i])

            {

                Edge ee = e[i];

                if(!vis[ee.v]&&d[ee.v]>d[ed.v]+ee.dis)

                {

                    d[ee.v] = d[ed.v]+ee.dis;

                    /*

                     *  最短路?

                    	p[ee.v] = MP(u,i);

                    */

                    q.push(Edge(ee.v,d[ee.v],ee.cost));

                }

            }

        }

    }



    void buildGraph(int m)

    {

        for(int i=0; i<m; i++)

        {

            int u,v,d,c;

            scanf("%d%d%d%d",&u,&v,&d,&c);

            addEdge(u,v,d,c);

            addEdge(v,u,d,c);

        }

    }



    Type getMinCost(int n)

    {

        int ans=0;

        for(int u=2; u<=n; u++) //首都不能?

        {

            int Min=INF;

            for(int j=head[u]; ~j; j=nxt[j])

            {

                Edge ee = e[j];

                if(d[u]==d[ee.v]+ee.dis && ee.cost<Min) //找??足?先距?最短，然后?用最低的那个最低?用

                    Min=ee.cost;

            }

            ans+=Min;

        }

        return ans;

    }

} dij;



int main()

{

    int n,m;

    while(~scanf("%d%d",&n,&m))

    {

        if(n==0 && m==0)

            break;

        dij.init(n);

        dij.buildGraph(m);

        dij.dijkstra(1,n,n);

        int ans=dij.getMinCost(n);

        printf("%d\n",ans);

    }

    return 0;

}