#include <bits/stdc++.h>
using namespace std;
int rec(string& s, int& index, vector<tuple<char, int, int>>& ops) {
//cerr << "REC: " << index << "\n";
for(int i = index; i < s.size(); i++) {
//cerr << s[i];
}
//cerr << "\n";
char op = s[index + 2];
int lchild;
int rchild;
index += 4;
//cerr << "\t" << s[index] << "\n";
if(s[index] == 'm') {
lchild = rec(s, index, ops);
}
else {
lchild = -1;
index++;
}
index++;
//cerr << "\t" << s[index] << "\n";
if(s[index] == 'm') {
rchild = rec(s, index, ops);
}
else {
rchild = -1;
index++;
}
index++;
//cerr << "\n\n";
ops.push_back(make_tuple(op, lchild, rchild));
return ops.size() - 1;
}
pair<int, int> get_size(vector<tuple<char, int, int>>& ops, int node) {
if(node == -1) {
return make_pair(0, 0);
}
//cerr << node << "<\n";
pair<int, int> left = get_size(ops, get<1>(ops[node]));
pair<int, int> right = get_size(ops, get<2>(ops[node]));
if(get<0>(ops[node]) == 'x') {
return make_pair(left.first + right.first + 1, min(left.second, right.second));
}
else {
return make_pair(min(left.first, right.first), left.second + right.second + 1);
}
}
int main() {
string input;
cin >> input;
//cerr << input << "\n";
vector<tuple<char, int, int>> ops;
int ix = 0;
rec(input, ix, ops);
//cerr << "OPS:\n\n";
for(tuple<char, int, int> t : ops) {
//cerr << get<0>(t) << " " << get<1>(t) << " " << get<2>(t) << "\n";
}
pair<int, int> sz = get_size(ops, ops.size() - 1);
cout << ops.size() + 1 - sz.first - sz.second;
return 0;
}
