import java.io.*;
public class Main {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int N = Integer.valueOf(br.readLine());
String number = br.readLine();
int sum = 0;
for(int i = 0; i < N; i++) {
sum += number.charAt(i) - '0';
}
System.out.print(sum);
}
}