#include <stdio.h>

int main(){
	int n;
	while(scanf("%d",&n) != EOF){
		float luck=0;
		int qiu=0;
		while(n--){
			int a;
			scanf("%d",&a);
			if(a>0){
				luck = luck + a*1.0/2.0;
			}else {
				luck = luck + a;
			}
			if(luck < 0){
				qiu ++;
			}
		}
		printf("%d\n",qiu);
	}
	return 0;
}