//Rahman ve Rahim olan Allah'ın adıyla
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ins insert
#define fi first
#define se second
#define int long long
#define mid (st+end)/2
#define spc <<" "<<
#define en <<"\n"
#define amin main
int32_t amin(){
ios_base::sync_with_stdio(false);cin.tie(0);
int n,q,a;cin>>n>>q;vector<int>strk(n,0);vector<int>lstn(n,0);int ans=0,lst=0;
for(int i=0;i<q;i++){
cin>>a;
if(a<0){
if(strk[abs(a)]>0){
strk[abs(a)]=0;
}
//cout<<a<<"\n";
}else{
if(strk[abs(a)]<0){
strk[abs(a)]=0;
}if(strk[abs(a)]!=0&&lstn[abs(a)]<lst){strk[abs(a)]=0;}
strk[abs(a)]++;lstn[abs(a)]=i;//cout<<"ed"<<abs(a)<<strk[abs(a)]<<"\n";
if(strk[abs(a)]!=1){
ans++;lst=i;//cout<<i;
}
}
}
cout<<ans;
}
