// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
using namespace std;
#define int long long
#define endl "\n";
const int N=2e5+5;
const int M=1e9+7;
int n , q , x , y , p[N] , cnt[N] , ind[N];
vector<vector<int>>a(N);
vector<int>pr(N);
vector<int>e;
vector<int>l(N);
vector<pair<int,int>>li(N);
void solve()
{
cin >> n >> q;
vector<int>k(n+1);
vector<int>ki(n+1);
int c=1;
for (int i=0;i<q;i++){
cin >> x;
if (x>0){
ki[x]--;
k[x]=max(k[x],ki[x])+1;
ki[x]=max(ki[x],x-x);
c=max(c,k[x]);
}
else{
x*=-1;
k[x]--;
ki[x]=max(k[x],ki[x])+1;
k[x]=max(k[x],x-x);
c=max(c,k[x]);
}
}
// for (int i=1;i<n;i++){
// c=max(c,mx[i]);
// }
cout << c-1 << endl;
}
signed main()
{
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);//DO NOT USE IN INTERACTIVE
cout << fixed<<setprecision(9);
int t=1;
// cin >> t;
for (int _=1;_<=t;_++){
solve();
}
}
// Fenwick Tree
// Sqrt Decomposition
// Segment Tree
