#include<stdio.h>
#include<math.h>
int main(){
	int n,m;
	while(scanf("%d",&n)!=EOF){
		int s=0,h=0;
		while(n--){
			scanf("%d",&m);
			if(m>0){s=s+0.5*m;}
			else{s=s+m;}
			if(s<0){h=h+1;}}
		printf("%d\n",h);
	}	
}