#include<stdio.h>
int A[1000];
int main(){
	int n,i;
	while(scanf("%d",&n)!=EOF){
		int l=0,q=0;
		for(i=0;i<n;i++){
			scanf("%d",&A[i]);
		}
	for(i=0;i<n;i++){
		if(A[i]>=0)
		l+=A[i]/2;
	    if(A[i]<0)
		l+=A[i];
		if(l<0)
		q+=1;
		
	}
	printf("%d\n",q);
	}
	return 0;
}