#include<iostream>

 #include<cstdio>

 #include<queue>

 #include<algorithm>

 #include<cmath>

 #include<ctime>

 #include<set>

 #include<cstring>

 #define inf 2147483647

 #define For(i,a,b) for(register int i=a;i<=b;i++)

 #define p(a) putchar(a)

 #define g() getchar()

 //by war

 //2017.20.27

 using namespace std;

 struct node

 {

     int n,v;

     node *next;

 }*e[];

 int D,P,C,F;

 int x,y,z;

 queue<int>q;

 bool vis[];

 int d[];

 int t;

 int cnt[];

 int ans=-inf;

 void in(int &x)

 {

     int y=;

     char c=g();x=;

     while(c<''||c>'')

     {

     if(c=='-')

     y=-;

     c=g();

     }

     while(c<=''&&c>='')x=x*+c-'',c=g();

     x*=y;

 }

 void o(int x)

 {

     if(x<)

     {

         p('-');

         x=-x;

     }

     if(x>)o(x/);

     p(x%+'');

 }

 void push(int x,int y,int v)

 {

     node *p;

     p=new node();

     p->n=y;

     p->v=v;

     if(e[x]==NULL)

     e[x]=p;

     else

     {

         p->next=e[x]->next;

         e[x]->next=p;

     }

 }

 void spfa(int x)

 {

     node *p;

     For(i,,C)

     d[i]=-inf;

     q.push(x);

     cnt[x]++;

     while(q.size()>)

     {

         t=q.front();

         vis[t]=true;

         p=e[t];

         while(p!=NULL)

         {

             if(d[t]+p->v>d[p->n])

             {

             d[p->n]=d[t]+p->v;

             if(!vis[p->n])

             {

             q.push(p->n);

             cnt[p->n]++;

             if(cnt[p->n]>C)

             {

                 puts("orz");

                 exit();

             }

             vis[p->n]=true;

             }

             }

             p=p->next;

         }

         vis[t]=false;

         q.pop();

     }

 }

 int main()

 {

     in(D),in(P),in(C),in(F);

     For(i,,C)

     push(,i,D);

     For(i,,P)

     {

     in(x),in(y);

     push(x,y,D);

     }

     For(i,,F)

     {

     in(x),in(y),in(z);

     push(x,y,D-z);

     }

     spfa();

     For(i,,C)

     ans=max(ans,d[i]);

     o(ans);

      return ;

 }