#include <iostream>
#include <string>
using namespace std;
int main(int argc, char** argv){
	string input;
	int sum = 0, n;
	cin >> n;
	cin.clear();
	while (cin.get() != '\n') {
		continue;
	}
	getline(cin, input);
	for (int i = 0; i < n; i++) {
		sum += input[i] - '0';
	}
	cout << sum << endl;
}