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

#include<queue>

#include<cstdlib>

#include<cstdio>

#include<cstring>



using namespace std;

const int maxn=4e4+100;

const int inf=0x3f3f3f3f;



struct Edge{

    int next;

    int to;

    int w;

    int  c;



}G[maxn];



int inq[maxn];

int dis[maxn];

int head[maxn];

int k=0;





void adde(int v,int to,int w,int c)//加?

{

    G[k].to=to;//第k条?指向的点

    G[k].w=w;//第k条?的??

    G[k].c=c;

    G[k].next=head[v];//与第k条??同起点的上一条?的?存位置

    head[v]=k++;

}



queue<int>Q;



void spfa(int s)

{

        while(!Q.empty())Q.pop();

        memset(inq,0,sizeof(inq));

        memset(dis,inf,sizeof(dis));

        dis[s] = 0;

        inq[s] = 1;

        Q.push(s);

        while(!Q.empty())

        {

                int u = Q.front();

                Q.pop();

                inq[u]=0;

                for(int i=head[u];i!=-1;i=G[i].next)//遍?以u?起点的所有?

                {

                        int v=G[i].to;

                        if(dis[v]>dis[u]+G[i].w)

                        {

                                dis[v]=dis[u]+G[i].w;

                                if(inq[v]==0)

                                {

                                    Q.push(v);

                                    inq[v]=1;

                                }

                        }

                }

                inq[u]=0;



        }

}



int main()

{

        int n,m;

        while(scanf("%d%d",&n,&m)!=EOF)

        {

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

                        return 0;

                memset(head,-1,sizeof(head));



                k=0;

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

                {

                            int a,b,c,d;

                            scanf("%d%d%d%d",&a,&b,&c,&d);

                            adde(a,b,c,d);

                            adde(b,a,c,d);

                }

                spfa(1);

                int ans=0;

                for(int i=2;i<=n;++i)

                {

                        int mi=inf;

                        for(int j=head[i];j!=-1;j=G[j].next)

                        {

                                if(dis[G[j].to]+G[j].w==dis[i]&&G[j].c<mi)

                                        mi=G[j].c;

                        }

                        ans+=mi;

                }

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

        }

        return 0;



}

// Faster C++ solution for the same problem (measured speedup: 1.2781819352732153x):
#include<cstdio>

#include<iostream>

#include<algorithm>

#include<vector>

#include<queue>

#define MAX_V 10006

#define INF 0x3fffffff

using namespace std;

struct edge{

    int to,cost,dis;

    };

typedef pair<int,int> P;

int V;

vector<edge> G[MAX_V];

int d[MAX_V];



void dij(int s){

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

    fill(d,d+V,INF);

    d[s]=0;

    que.push(P(0,s));

    while(!que.empty()){

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

        int v=p.second;

        if(d[v]<p.first)continue;

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

            edge e=G[v][i];

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

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

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

            }

        }

    }

    int ans=0;



    for(int i=1;i<V;i++){

        int mimcost=INF;

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

            if(d[G[i][j].to]+G[i][j].cost==d[i]&&G[i][j].dis<mimcost){



                mimcost=G[i][j].dis;

                //cout<<mimcost<<endl;

            }

        }

        //cout<<mimcost<<endl;

        ans+=mimcost;

    }

    cout<<ans<<endl;



}



int main(){

   // freopen("1.txt","r",stdin);

    int M;

    while(cin>>V>>M){

        if(V==0&&M==0)break;

        for(int i=0;i<V;i++)G[i].clear();

        while(M--){

            int a,b,t,c;

            cin>>a>>b>>t>>c;

            a--;b--;

            edge tmp;

            tmp.to=b;

            tmp.cost=t;

            tmp.dis=c;

            G[a].push_back(tmp);

            tmp.to=a;

            G[b].push_back(tmp);

        }

        dij(0);

    }

    return 0;

}