#include<bits/stdc++.h>
using namespace std;
// #include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision;
#define fio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long int
#define ull unsigned long long int  // ranges from (0 - twice of long long int)
#define rep(i,a,n) for (ll i=a;i<n;i++)
#define per(i,a,n) for (ll i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define vll vector<ll>
#define mod 1000000007LL
#define llpair pair<ll,ll>
#define INF 1000000000000000000ll
#define np next_permutation
#define PI acos(-1)
#define deb(x) cout<<#x<<" "<<x<<endl;
//ALWAYS USE ll DATA TYPE FOR INTEGER(FASTER THAN INTEGER AS WELL AS SOMETIMES WITHOUT USE LONG UR ANSWER WILL NOT ACCEPTED) && DOUBLE FOR DECIMAL VALUE
template<typename T> // for removing front element from the vector
void pop_front(std::vector<T> &v)
{
    if (v.size() > 0) {
        v.erase(v.begin());
    }
}
template<typename R> // for removing back element from the vector or can directly
void pop_back(std::vector<R> &v) // use vec.pop_back() function...
{
    if (v.size() > 0) {
        v.erase(v.begin()+v.size()-1);
    }
}

bool isprime(ll n)  //IN  O(sqrt(n))
{
    if(n<=1) return false;
    for(ll i=2;i*i<=n;i++)
        if(n%i==0)
            return false;

    return true;
}

vector<ll> factors(ll n){    //IN  O(sqrt(n))

    vll v;
    for(ll i=2;i*i<=n;i++)
    {
        if(n%i==0)
        {
            v.pb(i);
            if((n/i)!=i)
            v.pb(n/i);
        }
    }
    return v;
}

ll power(ll a, ll n,ll m)  // using Binary Exponential in TC O(logn)
{                     // Self Written By </ME> :)
    ll res=1;
    while(n)
    {
        if(n%2==1)
            res=((res%m) * (a)%m )  %m ,n--;
        else
            a=((a%m) *(a%m))%m, n/=2;
    }
    return res;
}

ll ts(ll arr[],int l,int r,int x) // ternary search to find x in sorted array arr
{
    
    while(l<=r)
    {
        ll mid1= l+(r-l)/3;
        ll mid2= r -(r-l)/3;
        if(arr[mid1]==x || arr[mid2]==x)
            return 1;
        if(x<arr[mid1])
            r=mid1-1;
        else if(x>arr[mid2])
            l=mid2+1;
        else
        {
            l=mid1+1;
            r=mid2-1;
        }
    }

    return -1;
}

vll f(ll n)
{
    vll res;
    for(ll i=1;i*i<=n;i++)
    {
        if(n%i==0)
        {
            if(i!=(n/i))
                res.pb(i), res.pb(n/i);
            else
                res.pb(i);
        }
    }

    return res;

}

ll gcd(ll a,ll b, ll n)
{
    if(a==b)
    {
        return (power(a,n,mod) + power(b,n,mod))%mod;
    }

    vll res = f(a-b);
    ll maxa=1;
    rep(i,0,res.size())
    {
        ll d= res[i];
        if (  ( power(a,n,d) + power(b,n,d) )%d ==0)
            maxa=max(maxa,d);
    }

    return maxa%mod;



}

int main() {
    fio;
    
    ll t=1;
    //cin>>t;
    while(t--)
    {
        ll a,b,m;
        cin>>a>>b>>m;
        ll arr[a+1]; rep(i,1,a+1) cin>>arr[i];
        ll brr[b+1]; rep(i,1,b+1) cin>>brr[i];
        ll res=INT_MAX;

        while(m--)
        {
            ll x,y,c; cin>>x>>y>>c;
            res=min(res,arr[x]+brr[y]-c);
        }

        


        ll mina = *min_element(arr+1,arr+b+1);
        ll minaa= *min_element(brr+1,brr+b+1);
        mina= mina+minaa;
        cout<<min(res,mina)<<"\n";
    }
    
   
   return 0;
}


Measured memory_bytes: 1792