#include<cstdio>
#include<iostream>
#include<map>
#include<set>
#include<vector>
#include<cstring>
#include<cassert>
#include<sstream>
#include<cmath>
#include<algorithm>
#include<queue>
#include<limits>
#include<ctime>
#include<stack>
#include<bits/stdc++.h>
#include<string>
#include<stdlib.h>
#include<stdio.h>
typedef long long ll;

using namespace std;

int main(){
	ll a,b,m;
	cin>>a>>b>>m;
	ll x[a],y[b],mins1=100005,mins2=100005;
	for(int i=0;i<a;i++){
		cin>>x[i];
		mins1=min(mins1,x[i]);
	}
	for(int i=0;i<b;i++){
		cin>>y[i];
		mins2=min(mins2,y[i]);
	}
	ll mins=mins1+mins2;
	for(int i=0;i<m;i++){
		ll d,e,f,now;
		cin>>d>>e>>f;
		now=x[d-1]+y[e-1]-f;
		mins=min(now,mins);
	}
	cout<<mins;
}


#include <bits/stdc++.h>

#define debug(...) fprintf(stderr, __VA_ARGS__)

#ifndef AT_HOME
#define getchar() IO::myGetchar()
#define putchar(x) IO::myPutchar(x)
#endif

namespace IO {
	static const int IN_BUF = 1 << 23, OUT_BUF = 1 << 23;

	inline char myGetchar() {
		static char buf[IN_BUF], *ps = buf, *pt = buf;
		if (ps == pt) {
			ps = buf, pt = buf + fread(buf, 1, IN_BUF, stdin);
		}
		return ps == pt ? EOF : *ps++;
	}

	template<typename T>
	inline bool read(T &x) {
		bool op = 0;
		char ch = getchar();
		x = 0;
		for (; !isdigit(ch) && ch != EOF; ch = getchar()) {
			op ^= (ch == '-');
		}
		if (ch == EOF) {
			return false;
		}
		for (; isdigit(ch); ch = getchar()) {
			x = x * 10 + (ch ^ '0');
		}
		if (op) {
			x = -x;
		}
		return true;
	}

	inline int readStr(char *s) {
		int n = 0;
		char ch = getchar();
		for (; isspace(ch) && ch != EOF; ch = getchar())
			;
		for (; !isspace(ch) && ch != EOF; ch = getchar()) {
			s[n++] = ch;
		}
		s[n] = '\0';
		return n;
	}

	inline void myPutchar(char x) {
		static char pbuf[OUT_BUF], *pp = pbuf;
		struct _flusher {
			~_flusher() {
				fwrite(pbuf, 1, pp - pbuf, stdout);
			}
		};
		static _flusher outputFlusher;
		if (pp == pbuf + OUT_BUF) {
			fwrite(pbuf, 1, OUT_BUF, stdout);
			pp = pbuf;
		}
		*pp++ = x;
	}

	template<typename T>
	inline void print_(T x) {
		if (x == 0) {
			putchar('0');
			return;
		}
		static int num[40];
		if (x < 0) {
			putchar('-');
			x = -x;
		}
		for (*num = 0; x; x /= 10) {
			num[++*num] = x % 10;
		}
		while (*num){
			putchar(num[*num] ^ '0');
			--*num;
		}
	}

	template<typename T>
	inline void print(T x, char ch = '\n') {
		print_(x);
		putchar(ch);
	}

	inline void printStr_(const char *s, int n = -1) {
		if (n == -1) {
			n = strlen(s);
		}
		for (int i = 0; i < n; ++i) {
			putchar(s[i]);
		}
	}

	inline void printStr(const char *s, int n = -1, char ch = '\n') {
		printStr_(s, n);
		putchar(ch);
	}
}
using namespace IO;

const int N = 100005;

int n, m, q, a[N], b[N];

void solve() {
	read(n), read(m), read(q);
	for (int i = 1; i <= n; ++i) {
		read(a[i]);
	}
	for (int i = 1; i <= m; ++i) {
		read(b[i]);
	}
	int ans = *std::min_element(a + 1, a + 1 + n) + *std::min_element(b + 1, b + 1 + m);
	for (int i = 1; i <= q; ++i) {
		int x, y, c;
		read(x), read(y), read(c);
		ans = std::min(ans, a[x] + b[y] - c);
	}
	print(ans);
}

int main() {
	int T = 1;
	// read(T);
	while (T--) {
		solve();
	}
}
