process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = []
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});

reader.on('line', (line) => {
  lines.push(line);
});

reader.on('close', () => {
 var abm = lines[0].split(' ');
 var a = Number(abm[0]);
 var b = Number(abm[1]);
 var m = Number(abm[2]);
 var kouho = [];
 var wariinfo = [];

 var rei = lines[1].split(' ');
 rei = rei.map(function(str) { return Number(str)});
 var renji = lines[2].split(' ');
 renji = renji.map(function(str) { return Number(str)});

 for(i=3; i<m+3; i++){
   var info = lines[i].split(' ');
   var a = Number(info[0]);
   var b = Number(info[1]);
   var c = Number(info[2]);

   var sum = rei[a-1] + renji[b-1] - c;
   kouho.push(sum);
 }
  var min = rei.sort((a, b)=> a - b)[0];
  min = min +  renji.sort((a, b)=> a - b)[0];
  kouho.push(min);
  min = kouho.sort((a, b)=> a - b)[0];
  console.log(min)
});