427A - Police Recruits.

#include<bits/stdc++.h>

using namespace std;

int main()

{

  long long int n;

  cin>>n;

  int crime=0;

  int man=0,un=0;

  for(long long int i=0;i<n;i++)

  {

      int t;

      cin>>t;

      if(t==-1)

      {

          crime++;

          if(man<crime)

          {

              un++;

              crime--;

          }

      }

      else

      {

          man+=t;

      }

  }

  cout<<un<<endl;

}