#include<stdio.h>

int main(){
	int n;
	int i;
	int num[1000];
	int luck,qiu;
	while(scanf("%d",&n)!=EOF){
		luck = 0;
		qiu = 0;
		for ( i=0; i<n; i++ ){
			scanf("%d",&num[i]);
	
			if( num[i] > 0){
				num[i] = num[i]/2;
			}
			luck += num[i];
			if( luck < 0){
				qiu += 1;
			}
		}
		printf("%d\n",qiu);
		
		
	}
	
}