# include<stdio.h>
int main(void){
    int n,i,s=0,m=0;
    int a[10000];
	while(scanf("%d",&n)!=EOF){
		for(i=0;i<n;++i){
			scanf("%d",&a[i]);
			if(a[i]>0)
			s=s+a[i]/2.0;
			else
			s+=a[i];
			if(s<0)
			m+=1;
		}
		printf("%d\n",m);
		m=0;
		s=0;
	}
}