#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cassert>

using namespace std;

const int inf = 1e9;

int main(){
	vector<pair<string, int> > v(1, make_pair(string(), 0));
	char c;
	int i = 0;
	while (cin.get(c)) {
		if (c == '<') {
			cin.get(c);
			if (c == '/')
				v[i].second = -1;
			else {
				v[i].second = 1;
				v[i].first += c;
			}
			while (cin.get(c)) {
				if ((c == '>') || (c == ' '))
					break;
				v[i].first += c;
			}
		}
		if (c == '>') {
			i++;
			v.push_back(make_pair(string(), 0));
			v.resize(i + 1);
		}
	}
	int n = v.size() - 1;
	if (n == 0) {
		cout << 0;
		return 0;
	}

	vector <vector <int> > dp(n, vector <int>(n, inf));




	for (int i = 0; i <= n - 1; i++) {
		if (i == n - 1) {
			dp[n - 1][n - 1] = 1;
			break;
		}
		dp[i][i] = 1;
		if ((v[i].first == v[i + 1].first) && (v[i].second == 1) && (v[i + 1].second == -1))
			dp[i][i + 1] = 0;
		else
			dp[i][i + 1] = 2;
	}

	for (int len = 3; len <= n; len++)
		for (int l = 0; l <= n - len; l++) {
			int r = l + len - 1;
			if ((v[l].first == v[r].first) && (v[l].second == 1) && (v[r].second == -1)) {
				for (int x = l; x < r; x++)
					dp[l][r] = min(dp[l][r], dp[l][x] + dp[x + 1][r]);

				dp[l][r] = min(dp[l][r], dp[l + 1][r - 1]);
			}
			else
				for (int x = l; x < r; x++)
					dp[l][r] = min(dp[l][r], dp[l][x] + dp[x + 1][r]);


		}

	cout << dp[0][n - 1];
	return 0;
}