123

#include<iostream>
using namespace std;
int k=0;
typedef struct tree {
	int data;
	tree *l,*r;
}treek,*treem;
void shu(treem &t) {
	t=new treek;
	int n=0;
	cin>>n;
	if(n==-1) {
		t=NULL;
		return;
	} else {
		t->data=n;
		shu(t->l);
		shu(t->r);
	}
}
void chu(treem &t,int q) {
	if(t==NULL) {
		return;
	} else {
		if(t->l==NULL&&t->r==NULL&&q==1) {
			k+=t->data;
		}
		if(t->l!=NULL) {
			chu(t->l,1);
		}
		if(t->r!=NULL) {
			chu(t->r,0);
		}
	}
}
int main() {
	treem t;
	shu(t);
	chu(t,0);
	cout<<k;
	return 0;
}