#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define rep(i, a, b) for(int i=(a); i<(b); i++)
#define sz(x) (int)x.size()
#define de(x) cout<< #x<<" = "<<x<<endl
#define dd(x) cout<< #x<<" = "<<x<<" "
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

const int N=101010;
int n,m;
int cc[N];
ll dis[N];
bool vis[N];
vector<pii> g[N];
pair<pii, pii> e[N];

void spfa() {
    vi q;q.pb(1);
    memset(dis,0x3f,sizeof(dis));
    memset(vis,0,sizeof(vis));
    dis[1]=0;vis[1]=1;
    rep(i,0,sz(q)) {
        int u=q[i];vis[u]=0;
        rep(j,0,sz(g[u])) {
            int v=g[u][j].fi, w=g[u][j].se;
            if(dis[v]>dis[u]+w) {
                dis[v]=dis[u]+w;
                if(!vis[v]) {
                    vis[v]=1;
                    q.pb(v);
                }
            }
        }
    }
}

int main() {
    while(~scanf("%d%d",&n,&m)) {
        if(n==0&&m==0) break;
        ///init
        rep(i,0,n+1) g[i].clear();
        ///read
        rep(i,1,m+1) {
            int u,v,w,c;scanf("%d%d%d%d",&u,&v,&w,&c);
            g[u].pb(mp(v, w));
            g[v].pb(mp(u, w));
            e[i]=mp(mp(u, v), mp(w, c));
        }
        ///solve
        spfa();
        memset(cc,0x3f,sizeof(cc));
        rep(i,1,m+1) {
            int u=e[i].fi.fi, v=e[i].fi.se;
            int w=e[i].se.fi, c=e[i].se.se;
            if(dis[u]+w==dis[v]) cc[v]=min(cc[v], c);
            if(dis[v]+w==dis[u]) cc[u]=min(cc[u], c);
        }
        int ans=0;
        rep(i,2,n+1) ans+=cc[i];
        printf("%d\n",ans);
    }
    return 0;
}