#include<stdio.h>
int main (){
int n;
int temp=0,total=0;
while(scanf("%d",&n)!=EOF){
while(n--){
float P_a;
int a;
scanf("%d",&a);
if(a>0){
if(a%2==1){
P_a=a/2+0.5;}
if(a%2==0){
P_a=a/2;}
}
else{
P_a=a;
}
temp=temp+P_a;
if(temp<0){
total=total+1;
}
}
printf("%d\n",total);
total=0;
temp=0;}
}