#include <iostream>
using namespace std;

int main() {
    int x;
    cin >> x;
    int hundreds = x / 100;
    int tens = (x / 10) % 10;
    int units = x % 10;
    int S = hundreds + tens + units;
    cout << S << endl;
    return 0;
}    
/**************************************************************
	Problem: 1027
	User: fuyijun
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/