#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <set>
#include <map>
#include <vector>
#include <string>

using namespace std;

string str;

int tab[110][110];

void doit(int beg, int end)
{
	if(beg == end) {tab[beg][end] = 0; return;}
	int best = 0;
	for(int x = beg; x <= end; x++)
	{
		int val = tab[beg][x]+tab[x][end];
		if(val > best) best = val;
	}
	if((str[beg] == '(' && str[end-1] == ')') ||
	 (str[beg] == '[' && str[end-1] == ']')) {
		int val = 2+tab[beg+1][end-1];
		if(val > best) best = val;
	}
	tab[beg][end] = best;
}

void setup()
{
	memset(tab,0xCC, sizeof(tab));
	for(int len = 0; len <= str.length(); len++)
		for(int beg = 0; beg + len <= str.length(); beg++)
			doit(beg, beg+len);
}

void run()
{
	getline(cin, str);
	if(str == "end")
		exit(0);
	setup();
	cout << tab[0][str.length()] << endl;
}

int main()
{
	while(1) run();
}