#include<stdio.h>
int main()
{
int n,a,i;
int xin,qiu;
while(scanf("%d",&n)!=EOF){
xin=0;
qiu=0;
for(i=1;i<=n;i++){
	scanf("%d",&a);
   if(a>0){
    xin=xin+a/2;
   if(xin<0)
    qiu+=1;
  }
 else if(a<=0){
	xin=xin+a;
	if(xin<0)
	qiu+=1;
     }

}
printf("%d\n",qiu);
}
	return 0;
}