#include <iostream>
#include <vector>
#include <cstdlib>
using namespace std;
int main() {
int N, Q;
if (!(cin >> N >> Q)) return 0;
/* state[p] : 1 = p is ahead of Anika, 0 = behind */
vector<unsigned char> state(N, 1);
/* lastEpoch[p] : last epoch when p was ahead of Anika */
/* lastEpoch[p] = epoch + 1 means p was behind in this epoch */
/* lastEpoch[p] = epoch means p was ahead in this epoch */
vector<int> lastEpoch(N, 0);
long long epoch = 0; // how many laps Anika has already run
long long laps = 0; // answer we build
while (Q--) {
int x; cin >> x;
int p = std::abs(x); // runner index (1 … N-1)
bool needAhead = (x > 0); // event requires: before it, p is ahead?
/* current status of p */
bool aheadNow = (lastEpoch[p] == epoch) ? state[p] : true;
if (aheadNow != needAhead) { // impossible ⇒ force one lap
++laps;
++epoch; // after a lap everybody is ahead
aheadNow = true;
}
/* flip relative order according to the event */
state[p] = !needAhead; // becomes behind or ahead
lastEpoch[p] = epoch; // updated this epoch
}
cout << laps << '\n';
return 0;
}
