#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cctype>
#include <string>
#include <queue>
#include <unordered_set>
#include <deque>
#include <numeric>
#include <cmath>
#include <unordered_map>
#include <set>
using namespace std;
#pragma GCC optimize("O3")
#pragma GCC optimization("Ofast,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
typedef long long ll;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, q;
cin >> n >> q;
vector<pair<int, int>> over(n, {-1, 0});
int ans = 0;
for (int i = 0; i < q; ++i) {
int x;
cin >> x;
if (x < 0) {
over[-x] = { -1, ans };
} else {
if (over[x].second != ans || over[x].first == -1) {
over[x] = { 1, ans };
} else {
ans++;
over[x] = { 1, ans };
}
}
}
cout << ans << '\n';
}
