#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main() {
int N, Q; cin >> N >> Q;
vector<bool> im_in_front(N, false);
vector<int> laps(N, 0);
vector<int> counter(N, -1);
while (Q--) {
int raw; cin >> raw;
int i = abs(raw) - 1;
bool im_surpassing = raw > 0;
counter[i]++;
// if (im_in_front[i] && im_surpassing) laps[i]++;
//
// im_in_front[i] = im_surpassing;
}
// cout << *max_element(laps.begin(), laps.end()) << endl;
cout << max(0, *max_element(counter.begin(), counter.end())) << endl;
}
