function main(input = ``) {
  let lines = input.split('\n');

  let [numBeansPerPack, numPacks, numPeople] = lines[0]
    .split(' ')
    .map((val) => parseInt(val));

  let ages = lines[1].split(' ').map((val) => parseInt(val));

  return `${ages.reduce((numBeans, age) => {
    return numBeans - age;
  }, numBeansPerPack * numPacks)}`;
}

const { readFileSync, existsSync } = require('fs');
const stdin = '/dev/stdin';

if (existsSync(stdin)) {
  const input = readFileSync(stdin, 'utf8');
  console.log(main(input));
}

module.exports = main;