#include <queue>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
using namespace std;const int MAXN = 105;
const int MAXE = 10005;
const int MAX_COST = 10005;
const int inf = 0x3f3f3f3f;typedef struct _node
{int v, next;int l, c;
}N;
N edge[MAXE];
int cntEdge, head[MAXN];typedef struct _no
{int v;int c, dis;_no(): dis(inf) {}_no(int a, int b, int c1): v(a), dis(b), c(c1) {} friend bool operator < (const struct _no &n1, const struct _no &n2){return n1.dis > n2.dis;}
}priN;void init()
{cntEdge = 0;for(int i = 0; i < MAXN; i++)head[i] = -1;
}void addEdge(int u, int v, int l, int c)
{edge[cntEdge].v = v;edge[cntEdge].l = l;edge[cntEdge].c = c;edge[cntEdge].next = head[u];head[u] = cntEdge++;
}int dis[MAXN];
int dijkstra(int s, int n, int tol)//1是起点，n是终点
{int vst[MAXN] = {0};for(int i = 0; i <= n; i++)dis[i] = inf;priority_queue<priN> Q;Q.push(priN(s, 0, 0));//dis[s] = 0;while(!Q.empty()){priN pre = Q.top();Q.pop();if(pre.v == n)return pre.dis;for(int f = head[pre.v]; f != -1; f = edge[f].next){int son = edge[f].v;int l = edge[f].l;int c = edge[f].c;if(pre.c + c <= tol){//dis[son] = dis[pre.v] + l;Q.push(priN(son, pre.dis + l, pre.c + c));}}}return -1;
}int main(void)
{
#ifndef ONLINE_JUDGEfreopen("in.txt", "r", stdin);
#endifint n, tol;while(scanf("%d", &tol) == 1){int m;scanf("%d %d", &n, &m);init();int u, v, l, c;for(int i = 0; i < m; i++){scanf("%d %d %d %d", &u, &v, &l, &c);addEdge(u, v, l, c);}int sol = dijkstra(1, n, tol);printf("%d\n", sol);}return 0;
}