#include<stdio.h>
int main(void){
int m,n;
while(scanf("%d",&m)!=EOF){
 int sum=0;
 int t=0;
for(int i=1;i<=m;i++){
scanf("%d",&n);
if(n>0)sum=sum+n/2;
if(n<0)sum=sum+n;
if(sum<0)t++;

}
printf("%d\n",t);

}
return 0;
}