#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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