#include<stdio.h>

int main() {
	int n;
	int a;

	while(scanf("%d",&n) != EOF) {
		int iRet = 0;
		double iTemp = 0;

		for(int i=0; i<n; i++) {
			scanf("%d",&a);
			if(a<=0) iTemp = iTemp + a;
			if(a>0) iTemp = iTemp + a/2.0;
			if(iTemp < 0) iRet++;
		}
		printf("%d\n",iRet);
	}
	return 0;
}