maximum element hackerrank solution
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <stack>
using namespace std;
int main() {
stack<int> max;
stack<int> s;
max.push(0);
int n;
cin>>n;
while (n--){
int a;
cin>>a;
if(a==1){
cin>>a;
if(a>=max.top()) max.push(a);
s.push(a);
}
else if(a==2){
if(s.top()==max.top()) max.pop();
s.pop();
}
else if(a==3) cout<<max.top()<<endl;
}
return 0;
}