#include<stdio.h>
int main(){
	int T,n,m,a[10000],k,i,l;
	while(scanf("%d",&T)!=EOF){
	l=0;k=0;
	for(i=0;i<T;i++){
		scanf("%d",&a[i]);
		if(a[i]<0){
			k+=a[i];}
		else
			k+=a[i]/2;
		if(k<0)
			l+=1;}
		printf("%d\n",l);
}
	return 0;
}