/**
 *    author:  NEZZ
**/
#include <bits/stdc++.h>
#define rep(i,a,b) for (int i=a;i<b;i++)
#define rep2(i,a,b) for (int i=a;i>=b;i--)
#define mod 1000000007
#define f first
#define s second
#define endl '\n'
#define ll long long
#define pii pair <int,int>
#define pll pair <ll,ll>
#define vi vector <int>
#define vl vector <ll>
#define vll vector < pll >
#define vii vector < pii >
#define vb  vector <bool>
#define pb push_back
#define mk make_pair
#define sz(a) a.size()
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define input freopen("intput","r",stdin)
#define output freopen("output","w",stdout)
#define fastIO ios_base::sync_with_stdio (0),cin.tie(0)
#define debug input,output


using namespace std;
void affiche (int t[],int n){ rep (i,0,n) cout<<t[i]<<" ";cout<<endl;}
void afficheV (vi t){rep (i,0,sz(t))cout<<t[i]<<" ";cout<<endl;}

int main (){
 fastIO;
  int n,d;
  cin>>n>>d;
  int t[n];
  ll sum[n];
  bool cond=true;
  int c=0;
  rep (i,0,n){
  cin>>t[i];
   if (i==0)
     sum[i]=t[i];
   else sum[i]=sum[i-1]+t[i];
   if (t[i]==0){
    c+=(sum[i]<0);
   }
   if (sum[i]>d)
    cond=false;
  }
  if (cond)
       cout<<c;
else cout<<-1;

}