include

using namespace std;

int main() {

char c[8];
bool d[8];
int a = 0;
for (int i = 0; i <= 7; i++) {
	cin >> c[i];
	if (c[i] == '1') {
		d[i] = true;
	} else {
		d[i] = false;
	}
}
for (int i = 0; i <= 7; i++) {
	if (d[i] == true) {
		a++;
	}
}
printf("%d", a);
return 0;

}