// 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: 1.3640772617328227x):
#include<cstdio>

#include<cstring>

#include<algorithm>

#include<vector>

#include<queue>



#define N 10010



struct Edge{

	int y;

	int z;

	int w;

	Edge(){}

	Edge(int y,int z,int w):y(y),z(z),w(w){}

	bool operator <(const Edge&_x)const{

		return this->z>_x.z || (this->z==_x.z && this->w>_x.w);

	}

};

#define Node Edge



std::vector<Edge> v[N];



void Dijkstra(int&);



int main(){

	while(true){

		int n,m;

		scanf("%d%d",&n,&m);

		if(!(n||m))

			break;

		for(int i=1;i<=n;i++)

			v[i].clear();

		while(m--){

			int x,y,z,w;

			scanf("%d%d%d%d",&x,&y,&z,&w);

			v[x].push_back(Edge(y,z,w));

			v[y].push_back(Edge(x,z,w));

		}

		int ans=0;

		Dijkstra(ans);

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

	}

	return 0;

}



void Dijkstra(int &ans){

	std::priority_queue<Node> q;

	q.push(Node(1,0,0));

	bool vis[N]={};

	while(q.size()){

		int x=q.top().y,z=q.top().z,w=q.top().w;

		q.pop();

		if(vis[x])

			continue;

		vis[x]=true;

		ans+=w;

		for(auto p:v[x])

			q.push(Node(p.y,z+p.z,p.w));

	}

}