#include<iostream>
#include<sstream>
#include<algorithm>
#include<climits>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<cfloat>
#include<functional>
#include<map>
#include<string>
#include<cstring>
#include<vector>
#include<queue>
#include<stack>
#include<deque>
#include<set>
#include<bitset>
#include<list>
#include<numeric>
#include<complex>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<long long, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<long long, long long> ll_ll;
typedef pair<double, double> d_d;
typedef vector<int> Vint;

#define PI 3.141592653589793238462643383279
#define mod 1000000007LL
#define rep(i, n) for(i = 0;i < n;++i)
#define rep1(i, n) for(i = 1;i < n;++i)
#define rep2d(i, j, n) for(i = 0;i < n;++i)for(j = i + 1;j < n;++j)
#define per(i, n) for(i = n - 1;i > -1;--i)
#define int(x) int x; scanf("%d",&x)
#define int2(x, y) int x, y; scanf("%d%d",&x, &y)
#define int3(x, y, z) int x, y, z; scanf("%d%d%d",&x, &y, &z)
#define scn(n, a) rep(i, n)cin >> a[i]
#define sc2n(n, a, b) rep(i, n)cin >> a[i] >> b[i]
#define pri(x) cout << x << "\n"
#define pri2(x, y) cout << x << " " << y << "\n"
#define pri3(x, y, z) cout << x << " " << y << " " << z << "\n"
#define pb push_back
#define mp make_pair
#define all(a) (a).begin(),(a).end()
#define endl "\n"
#define kabe puts("---------------------------")
#define kara puts("")
#define debug(x) cout << " --- " << x << "\n"
#define debug2(x, y) cout << " --- " << x << " " << y << "\n"
#define debug3(x, y, z) cout << " --- " << x << " " << y << " " << z << "\n"
#define X first
#define Y second
#define eps 0.0001
#define prid(x) printf("%.15lf\n", x)

struct edge{
  int to, cost;
};

vector<edge> G[20];
ll longinf = 123451234512345LL;

ll dijkstra(int v, int e, int r, int g){   //(vertex, edge, start, goal)
  ll res = 0;
  int i, j;
  ll d[v];
  rep(i, v)d[i] = longinf;
  d[r] = 0LL;
  priority_queue<ll_i, vector<ll_i>, greater<ll_i> > Q;
  Q.push(mp(0LL, r));
  for(;!Q.empty();){
    ll_i now = Q.top();
    Q.pop();
    if(d[now.Y] < now.X)continue;
    rep(i, G[now.Y].size()){
      edge tmp = G[now.Y][i];
      if(d[tmp.to] > d[now.Y] + tmp.cost){
        d[tmp.to] = d[now.Y] + tmp.cost;
        Q.push(mp(d[tmp.to], tmp.to));
      }
    }
  }
  res = d[g];
  return res;
}

signed main(void){
  int i, j, k;
  for(int testcase = 0;testcase < 1234567;testcase++){
    int2(n, m);
    int a, b, c, d;
    rep(i, m){
      scanf("%d,%d,%d,%d", &a, &b, &c, &d);
      --a; --b;
      G[a].pb((edge){b, c});
      G[b].pb((edge){a, d});
    }
    
    scanf("%d,%d,%d,%d", &a, &b, &c, &d);
    --a; --b;
    pri(c - d - dijkstra(n, m, a, b) - dijkstra(n, m, b, a));

/*/

//*/ break;
  }
  return 0;
}