function Main(input) {
  let num = input.replace(/[^0-9]/g, '');
  if (num === "") {
    console.log(0);
  } else {
    let array = num.split('').map(Number);
    let sum = array.reduce((a,b)=>a+b);
    console.log(sum);
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));