#include<cstdio>
#include<queue>
#include<vector>
struct Edge{
    int u,v;
    long long c,d;
    Edge(int u,int v,long long c,long long d):u(u),v(v),c(c),d(d){}
    Edge(){}
};
std::vector<int>g[100005];
Edge edge[200005];
int fix[100005];
long long dis[100005];
int inEdge[100005];
int used[200005];
struct Node{
    int u;
    long long value;
    Node(int u,long long value):u(u),value(value){}
    bool operator < (const Node& other)const{
        return value>other.value;
    }
};

long long dijkstra(int s,int t,int n){
    for(int i = 1; i <= n; i++) fix[i] = 0, dis[i] = 1e17+7;
    std::priority_queue<Node>Q;
    dis[s] = 0;
    Q.push(Node(s,0));
    while(Q.size()!=0){
        while(Q.size()!=0 && fix[Q.top().u]==1) Q.pop();
        if(Q.size()==0) break;
        Node cur = Q.top(); 
        Q.pop();
        int u = cur.u;
        fix[u] = 1;
        for(int e: g[u]){
            long long cost = edge[e].c;
            int v = edge[e].v;
            if(used[e]) cost = edge[e].d;
            if(dis[v] > dis[u]+cost){
                inEdge[v] = e;
                dis[v] = dis[u]+cost;
                Q.push(Node(v,dis[v]));
            }
        }
    }
    int cur = t;
    while(cur!=s){
        int ue = inEdge[cur];
        int ve = -1;
        if(ue%2) ve = ue+1;
        else ve = ue-1;
        used[ue] = used[ve] = 1;
        cur = edge[ue].u;
    }
    return dis[t];
}

int main(){
    int n,m;
    scanf("%d%d",&n,&m);
    int total = 0;
    for(int i = 1; i <= m; i++){
        int u,v; long long c,d;
        scanf("%d%d%lld%lld",&u,&v,&c,&d);
        edge[++total] = Edge(u,v,c,d);
        g[u].push_back(total);
        edge[++total] = Edge(v,u,c,d);
        g[v].push_back(total);
    }
    long long ans = dijkstra(1,n,n);
    ans += dijkstra(n,1,n);
    printf("%lld\n",ans);
    return 0;
}