#include <stdio.h>
int main(){
	int n,i,a[1000000],j,x,z;
	while(scanf("%d",&n)!=EOF){
    i=1;x=0;z=0;j=0;
	while(i<=n){
	scanf("%d",&a[i]);
	j=a[i];
	if(j>0)
		x=x+j/2;
	else if(j<0)
		x=x+j;
	if(x<0)
		z=z+1;
	++i;
	}
	printf("%d\n",z);
}
	return 0;
}