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