# include<stdio.h>
int main(void){
	int a,i,m=0;
	double j=0;
	int n[100000];
	while(scanf("%d",&a)!=EOF){
		for(i=0;i<a;++i){
			scanf("%d",&n[i]);
			if(n[i]>0)
			   j=j+n[i]/2.0;
			else
			   j+=n[i];
			if(j<0)
			   m+=1;
		}
		printf("%d\n",m);
		m=0;
		j=0;
	}	
}