#include <iostream>
#include <queue>
#include <string>
using namespace std;
 
int main() {
	// your code goes here
	int n;
	cin>>n;
	int count=0;
	priority_queue<int, vector<int>, greater<int>>q;
	int min=1;//the next box needed to be removed
	bool ordered=true;
	for (int i=0; i<2*n; ++i){
		string s;
		cin>>s;
		if (s=="remove"){
			q.pop();
			++min;
		}
		if (s=="add"){
			int k;
			cin>>k;
			if (!q.empty() && k>q.top())ordered=false;
			q.push(k);
		}
		if (ordered==false && q.top()==min){
			//reorder them now
			ordered=true;
			++count;
		}
	}
	cout<<count;
	return 0;
}

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NwphZGQgMwphZGQgMgphZGQgMQpyZW1vdmUKYWRkIDQKcmVtb3ZlCnJlbW92ZQpyZW1vdmUKYWRkIDYKYWRkIDcKYWRkIDUKcmVtb3ZlCnJlbW92ZQpyZW1vdmU=

7
add 3
add 2
add 1
remove
add 4
remove
remove
remove
add 6
add 7
add 5
remove
remove
remove