#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <ll, ll> pii;
#define fi first
#define se second
#define pb push_back
const int MOD = 1e9 + 7;
const int MAX = 5e5 + 5;
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};
#define int ll
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, q; cin >> n >> q;
int ans = 0;
int prev[n + 5], pos[n + 5];
while(q--){
int x; cin >> x;
if(x > 0){
if(pos[x] == 1 && prev[x] == ans){
prev[x]++;
ans++;
pos[x] = 1;
}
else{
pos[x] = 1;
prev[x] = ans;
}
}
else{
x = -x;
pos[x] = 0;
prev[x] = ans;
}
}
cout << ans << endl;
return 0;
}
