#include<stdio.h>
#include<string.h>
#include<math.h>
int main(){
	int n;

	while(~scanf("%d",&n)){
		int luck=0,x=0;
		for(int i=0;i<n;++i){
			int a;
			scanf("%d",&a);
			if(a>0)
				luck=luck+a/2;
			else
				luck+=a;
			if(luck<0)
				x+=1;
		}
		printf("%d\n",x);
	}
}