My code is giving wrong answer on test cases 12, 20, 21, 23. I don't know what exception I am missing in my logic building, but since the test case is very large, I cannot possibly trace my code on that test case. Can someone please find a bug in my code?

int main(){

unsigned long int totalplants;
cin>>totalplants;
unsigned long long int* plants;
plants = new unsigned long long int [totalplants]; 
for (int i = 0; i < totalplants; i += 1) {
    cin>>plants [i];
}
stack <unsigned long long int> plantsdata; 
unsigned long int maxdays = 0;
for (int i = totalplants - 1; i >= 0; i -= 1) {
    if (plantsdata.empty() or plants[i] >= plantsdata.top())
        plantsdata.push(plants[i]);
    else {
        unsigned long int currentdays = 0;
        while (not plantsdata.empty() and plants[i] < plantsdata.top()) {
            currentdays += 1;
            plantsdata.pop();
        }
        if (currentdays > maxdays) maxdays = currentdays;
        plantsdata.push(plants[i]);
    }
}
cout<<maxdays;
return 0;

}