#include<stdio.h>
int main(){
int n,i;
int m=0;
int l=0;
int a[10000];
while(scanf("%d",&n)!=EOF){
for(i=0;i<n;i++){
scanf("%d",&a[i]);
if(a[i]>0){m=m+a[i]/2;}
else{m=m+a[i];}
if(m<0){l=l+1;}
}
printf("%d\n",l);
l=0;
m=0;
}
return 0;
}