#include<stdio.h>
int main(){
int n,m,s,a;
while(scanf("%d",&n)!=EOF){
s=0,a=0;
while(n--){
scanf("%d",&m);
s+=m>0?m/2:m;
a+=s<0?1:0;
}
printf("%d\n",a);
}
return 0;
}