#include<stdio.h>
int main(){
	int t,x,c;
	float a,b;
	while(~scanf("%d",&t)){
		b=0.0;
		c=0;
		for(x=1;x<=t;x++){
			scanf("%f",&a);
			if(a>=0){
				b=b+(a/2.0);
			}
			else b=b+a;
			if(b<0) c++;
		}
		printf("%d\n",c);
	}
}