1 /*
 2   spfa + 01背包
 3   dist[next][j]=min(dist[cur][j-v[cur][i].T]+v[cur][i].L) j={v[cur][i].T。。。maxCost}
 4   一维数组表示的是城市节点，二维表示的当前费用
 5   dist[i][j]表示经过i城市，费用为j时总的路径长度！
 6 */
 7 #include<iostream>
 8 #include<cstdio>
 9 #include<cstring>
10 #include<vector>
11 #include<queue>
12 #include<algorithm>
13 #define Max 0x3f3f3f3f
14 using namespace std;
15
16 struct node{
17    int D;
18    int L, T;
19    node(int D, int L, int T){
20       this->D=D;
21       this->L=L;
22       this->T=T;
23    }
24    node(){
25    }
26 };
27
28 node v[105][1000];
29 int cnt[105];
30 int dist[105][10005];
31 int vis[105];
32 queue<int>q;
33 int maxCost, R, N, S, D, L, T;
34
35 int spfa(){
36    int i;
37    while(!q.empty()){
38        int cur = q.front();
39        q.pop();
40        vis[cur]=0;
41        for(i=0; i<cnt[cur]; ++i){
42            int next=v[cur][i].D;
43            for(int j=v[cur][i].T; j<=maxCost; ++j)
44               if(dist[next][j]>dist[cur][j-v[cur][i].T]+v[cur][i].L){
45                  dist[next][j]=dist[cur][j-v[cur][i].T]+v[cur][i].L;
46                  if(!vis[next]){
47                    vis[next]=1;
48                    q.push(next);
49                  }
50              }
51        }
52    }
53 }
54
55 void bfs(int cur){
56    q.push(1);
57    memset(dist, 0x3f, sizeof(dist));
58    for(int i=0; i<105; ++i)
59       dist[1][i]=0;
60    vis[1]=1;
61    spfa();
62 }
63
64 int main(){
65    while(scanf("%d", &maxCost)!=EOF){
66        scanf("%d%d", &N, &R);
67        memset(cnt, 0, sizeof(cnt));
68        while(R--){
69           scanf("%d%d%d%d", &S, &D, &L, &T);
70           v[S][cnt[S]++]=node(D, L, T);
71        }
72        memset(vis, 0, sizeof(vis));
73        bfs(1);
74        int minDist=Max;
75        for(int i=1; i<=maxCost; ++i)
76           if(minDist>dist[N][i])
77               minDist=dist[N][i];
78        if(minDist!=Max)
79           printf("%d\n", minDist);
80        else printf("-1\n");
81    }
82    return 0;
83 }