#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define pb push_back
#define sz(a) (ll) a.size()
#define all(x) (x).begin(), (x).end()
#define rep(i, a, b) for(ll i=a; i<b; i++)
#define rrep(i, a, b) for(ll i=a; i>=b; i--)
#define vl vector<ll>
#define vpll vector<pair<ll, ll>>
#define vvl vector<vector<ll>>
#define pll pair<ll, ll>
ll n;
vector<bool> curr;
void f() {
cin >> n;
curr.assign(n, 0);
ll q, ans=0; cin >> q;
rep(i, 0, q){
ll x; cin >> x;
if(x<0){
curr[-x]=0;
} else {
if(curr[x]==1){
ans++;
curr.assign(n, 0);
curr[x]=1;
} else {
curr[x]=1;
}
}
}
cout << ans;
}
int main() {
int tc = 1;
// cin >> tc;
for (int i = 1; i <= tc; i++) {
// cout << '#' << i << endl;
f();
cout << endl;
}
}
