const readline = require('readline');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.question('', (input) => {
  const sumOfDigits = [...input].filter(c => c <= '9').reduce((sum, c) => sum + parseInt(c, 10), 0);
  console.log(sumOfDigits);
  rl.close();
});