function main(input) {
    a = input.charAt(0);
    b = input.charAt(1);
    c = input.charAt(2);
    n = 0;
    a==1 ? n++ : n=n;
    b==1 ? n++ : n=n;
    c==1 ? n++ : n=n;
    console.log(n)
}
main(require("fs").readFileSync("/dev/stdin","utf8"));
