#include <stdio.h>
 #include<stdlib.h>
 
int main(void) {
	int N;
	int sum=0;
	scanf("%d\n",&N);
	char* str = (char*)malloc(sizeof(char)*N);
	scanf("%s",str);
	for(int i=0; i<N; ++i){
		int tem = (int)str[i] - 48;
		sum += tem;
	}
	printf("%d",sum);
	return 0;
}