//  [cpp]
#include <bits/stdc++.h>

using namespace std;

#define REP(i, N) for (int i = 0; i < (int)N; i++)
#define FOR(i, a, b) for (int i = a; i < (int)b; i++)
#define ALL(x) (x).begin(), (x).end()
#define INF (1 << 30)
#define LLINF (1LL << 62)
#define DEBUG(...) debug(__LINE__, ":" __VA_ARGS__)

constexpr int MOD = 1000000007;
using ll = long long;
using Pii = pair<int, int>;
using Pll = pair<ll, ll>;

template <class T>
string to_string(T s);
template <class S, class T>
string to_string(pair<S, T> p);
string to_string(string s) { return s; }
string to_string(const char s[]) { return to_string(string(s)); }

template <class T>
string to_string(T v) {
  if (v.empty()) return "{}";
  string ret = "{";
  for (auto x : v) ret += to_string(x) + ",";
  ret.back() = '}';
  return ret;
}
template <class S, class T>
string to_string(pair<S, T> p) {
  return "{" + to_string(p.first) + "," + to_string(p.second) + "}";
}

void debug() { cerr << endl; }
template <class Head, class... Tail>
void debug(Head head, Tail... tail) {
  cerr << to_string(head) << " ";
  debug(tail...);
}

struct IO {
  static constexpr size_t buf_size = 1 << 18;
  char buf_in[buf_size], buf_out[buf_size];
  size_t pt_in = 0, pt_out = 0, tail_in = 0;
  char strs[1000][4];
  int ints[58];
  size_t num_digits(long long x) {
    if (x >= (long long)1e9) {
      if (x >= (long long)1e18) return 19;
      if (x >= (long long)1e17) return 18;
      if (x >= (long long)1e16) return 17;
      if (x >= (long long)1e15) return 16;
      if (x >= (long long)1e14) return 15;
      if (x >= (long long)1e13) return 14;
      if (x >= (long long)1e12) return 13;
      if (x >= (long long)1e11) return 12;
      if (x >= (long long)1e10) return 11;
      return 10;
    } else {
      if (x >= (long long)1e8) return 9;
      if (x >= (long long)1e7) return 8;
      if (x >= (long long)1e6) return 7;
      if (x >= (long long)1e5) return 6;
      if (x >= (long long)1e4) return 5;
      if (x >= (long long)1e3) return 4;
      if (x >= (long long)1e2) return 3;
      if (x >= (long long)1e1) return 2;
      return 1;
    }
  }
  IO() {
    load();
    for (int i = 0; i < 1000; ++i) {
      int j = i;
      strs[i][3] = 0;
      for (int t = 2; t >= 0; --t) {
        strs[i][t] = j % 10 + '0';
        j /= 10;
      }
    }
    for (int i = '0'; i <= '9'; ++i) {
      ints[i] = i - '0';
    }
  }
  ~IO() { flush(); }
  inline void load() {
    copy(buf_in + pt_in, buf_in + tail_in, buf_in);
    size_t width = tail_in - pt_in;
    tail_in = width + fread(buf_in + width, 1, buf_size - width, stdin);
    pt_in = 0;
  }
  inline void flush() {
    fwrite(buf_out, 1, pt_out, stdout);
    pt_out = 0;
  }
  inline void read(char& c) { c = buf_in[pt_in++]; }
  template <class T>
  inline void read(T& x) {
    if (pt_in + 32 > tail_in) load();
    char c;
    do {
      read(c);
    } while (c < '0');
    bool minus = 0;
    if (c == '-') {
      minus = 1;
      read(c);
    }
    x = 0;
    while (c >= '0') {
      x = x * 10 + ints[c];
      read(c);
    }
    if (minus) x = -x;
  }
  inline void write(char c) { buf_out[pt_out++] = c; }
  template <class T>
  inline void write(T x) {
    if (pt_out > buf_size - 32) flush();
    if (x < 0) {
      write('-');
      x = -x;
    }
    size_t digits = num_digits(x);
    size_t i;
    for (i = pt_out + digits; i > pt_out + 3; i -= 3) {
      memcpy(buf_out + i - 3, strs[x % 1000], 3);
      x /= 1000;
    }
    memcpy(buf_out + pt_out, strs[x] + 3 - (i - pt_out), i - pt_out);
    pt_out += digits;
  }
  inline void write(const char* s) {
    if (pt_out > buf_size - 32) flush();
    for (int i = 0; s[i] != 0; ++i) write(s[i]);
  }
  template <class T>
  inline void writeln(T x) {
    write(x);
    write('\n');
  }
} io;

int main() {
  int A, B, M;
  io.read(A);
  io.read(B);
  io.read(M);
  int a[100000], b[100000], mina = INF, minb = INF;
  REP(i, A) {
    io.read(a[i]);
    mina = min(mina, a[i]);
  }
  REP(i, B) {
    io.read(b[i]);
    minb = min(minb, b[i]);
  }
  int ans = mina + minb;
  while (M--) {
    int x, y, c;
    io.read(x);
    io.read(y);
    io.read(c);
    ans = min(ans, a[x - 1] + b[y - 1] - c);
  }
  io.writeln(ans);
  return 0;
}