// –Í‹[’n‹æ—\‘I2010 H. Road Construction

#include <iostream>
#include <vector>
#include <queue>
#include <cstring>

using namespace std;

typedef vector< vector< pair<int, pair<int, int> > > > graph;

class Node{
public:
	int pos, dist, cost;
	Node(int pos, int dist, int cost) : pos(pos), dist(dist), cost(cost) {}
	bool operator < (const Node &nd) const { 
		return make_pair(dist, cost) > make_pair(nd.dist, nd.cost); 
	}
};

int main(){
	int N, M;
	static int dist[10000];
	static bool visit[10000];
	while(cin >> N >> M, N){
		graph g(N);
		for(int i=0;i<M;i++){
			int u, v, d, c; cin >> u >> v >> d >> c;
			g[u-1].push_back(make_pair(v-1, make_pair(d, c)));
			g[v-1].push_back(make_pair(u-1, make_pair(d, c)));
		}
		int ans = 0;
		memset(dist, -1, sizeof(dist));
		memset(visit, false, sizeof(visit));
		dist[0] = 0;
		priority_queue<Node> qu; qu.push(Node(0, 0, 0));
		while(!qu.empty()){
			Node nd = qu.top(); qu.pop();
			int pos = nd.pos, d = nd.dist;
			if(dist[pos]!=-1 && dist[pos] < d) continue;
			if(visit[pos]) continue;
			visit[pos] = true;
			ans += nd.cost;
			for(int i=0;i<g[pos].size();i++){
				int next = g[pos][i].first;
				if(dist[next]==-1 || dist[next] >= dist[pos] + g[pos][i].second.first){
					dist[next] = dist[pos] + g[pos][i].second.first;
					qu.push(Node(next, dist[next], g[pos][i].second.second));
				}
			}
		}
		cout << ans << endl;
	}
}