#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#ifdef _debug
#include </home/tony/templates/debug.cpp>
#else
#define debug(...) 42
#endif
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define pb push_back
#define vi vector<int>
#define vt vector
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const int MOD = 1e9 + 7, inf = (int)2e9;
const ll infll = (ll)1e18;
void solve(){
int n,m;cin >> n >> m;
set<int> s;
int a = 0;
for(int i = 0; i < m; i++){
int u; cin >> u;
if(u < 0){
s.erase(-u);
}else{
if(s.count(u))a++, s = {u};
else s.insert(u);
}
}
cout << a << '\n';
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0);
solve();
}
