#include<stdio.h>

int main(){
	int n, i, a;
	double c = 0;

	while(~scanf("%d",&n)){
		int count = 0, sum =0;
		for(i = 0; i < n; i++){
			scanf("%d", &a);
			if(a > 0){
				c = a*1.0/2;
				sum = sum + c;
			}else{
				sum = sum + a;
			}
			if(sum < 0){
				count ++;
			}
		}printf("%d\n", count);
	}
	return 0;
}