#include<stdio.h>
#include<string.h>
#include<math.h>
int main(void){
int n,luck,qiu,m;
while(scanf("%d",&n)!=EOF){
	luck=0;
	qiu=0;
	while(n--){
		scanf("%d",&m);
	if(m>0)
		luck+=m/2;
	else
		luck+=m;
	if(luck<0)
		qiu++;
	}
	printf("%d\n",qiu);

}
}