#include <iostream>
using namespace std;
 
int main() {
    int N;
    cin >> N;
 
    int* A = new int[N];
 
    for (int i = 0; i < N; i++) {
        char c;
        cin >> c;         
        A[i] = c - '0';   
    }
 
    int sum = 0;
    for (int i = 0; i < N; i++) {
        sum += A[i];
    }
    cout << sum;
 
 
    return 0;
}
 
 
 
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