# include <stdio.h>
int main(){
	int n;
   	while(scanf("%d",&n)!=EOF){
	  int a,sum1=0,sum2=0;
	  while(n--){
	  scanf("%d",&a);
	  if(a<0){
	   sum1+=a;
	  }
	 if(a>0){
	 	sum1 += a/2.0;
	 }
	  if(sum1<0){
	  	sum2 +=1;
	  }
	  
}
      printf("%d\n",sum2);
}
	return 0;
}