codevs2645 Spore

/*
spfa + 判环
*/
#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#include<queue>
#define ll long long
using namespace std;
const int maxn = 20005;
const ll inf = 987654321234LL;
struct edge{
    int v;
    int w;
    int nxt;
}e[maxn*3];
int n,m;
int cnt,head[maxn],flag,vis[maxn],rd[maxn];
ll dis[maxn];
ll read(){
    char ch=getchar();
    ll x=0,f=1;
    while(!(ch>=‘0‘&&ch<=‘9‘)){if(ch==‘-‘)f=-1;ch=getchar();};
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+(ch-‘0‘);ch=getchar();};
    return x*f;
}
void ins(int u,int v,int w){
    cnt++;
    e[cnt].v = v;
    e[cnt].w = w;
    e[cnt].nxt = head[u];
    head[u] = cnt;
}
bool spfa(){
    for(int i = 0;i <= n;i++){
        dis[i] = inf;
        rd[i] = 0;    
    }
    dis[1] = 0;
    flag++;
    queue<int> q;
    int now,to;
    q.push(1);
    vis[1] = flag;
    rd[1] = 1;
    while(!q.empty()){
        now = q.front();
        q.pop();
        for(int i = head[now];i;i = e[i].nxt){
            to = e[i].v;
            if(dis[to] > dis[now] + e[i].w){
                dis[to] = dis[now] + e[i].w;
                if(vis[to] != flag){
                    vis[to] = flag;
                    q.push(to);
                    rd[to]++;
                    if(rd[to] > n) return false;
                }
            }
        }
        vis[now] = 0;
    }
    if(dis[n] >= inf) return false;
    else return true;
}
int main(){
    while(1){
        cnt = 0;
        n = read();
        m = read();
        if(!n && !m) break;
        for(int i = 1;i <= n;i++) head[i] = 0;
        int g1,g2,c1,c2;
        for(int i = 1;i <= m;i++){
            g1 = read();
            g2 = read();
            c1 = read();
            c2 = read();
            ins(g1,g2,c1);
            ins(g2,g1,c2);
        }
        if(spfa()) cout<<dis[n]<<endl;
        else cout<<"No such path"<<endl;
    }
    return 0;
}