#include <iostream>

int main() {
    int n;
    std::cin >> n;
    int sum = 0;

    sum += n % 10;
    n /= 10;
    sum += n % 10;
    n /= 10;
    sum += n % 10;
    n /= 10;
    sum += n;

    std::cout << sum;
    return 0;
}    
/**************************************************************
	Problem: 1390
	User: fuyijun
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/