#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstring>

#include<string>

#include<stack>

#include<queue>

#include<vector>

#include<algorithm>

#define N 10101010

using namespace std;

void in(int &x){

    register char c=getchar();x=;int f=;

    while(!isdigit(c)){if(c=='-') f=-;c=getchar();}

    while(isdigit(c)){x=x*+c-'';c=getchar();}

    x*=f;

}

int n,w,k,W[N],v[N],fa[N],f[],ans,g[N];

vector<int>V[];

int find(int u){return fa[u]==u?u:find(fa[u]);}

bool vis[N];

int main()

{

    in(n);in(w);in(k);

    for(int i=;i<=n;i++) in(v[i]),in(W[i]),fa[i]=i;

    for(int i=;i<=k;i++){

        int u,v,fu,fv;

        in(u);in(v);

        fu=find(u);fv=find(v);

        if(fu!=fv){

            fa[fu]=fv;

        }

    }

    for(int i=;i<=n;i++){

        fa[i]=find(i);

        if(fa[i]==i) g[++g[]]=i;

        V[fa[i]].push_back(i);

    }for(int i=;i<=g[];i++){

        for(int k=w;k>=;k--){

            for(int j=;j<V[g[i]].size();j++){

                int q=V[g[i]][j];

                if(k>=W[q]) f[k]=max(f[k],f[k-W[q]]+v[q]);//防止数组越界

            }

        }

    }printf("%d\n",f[w]);

    return ;

}