#include <string>
#include <iostream>
using namespace std;

int longest[101][101];
int n;

string s;

int main()
{
  while (true)
  {
    cin >> s;
    if (s == "end")
      break;

    //cout << "\"" << s << "\"" << endl;
    n = s.length();

    int l = 1;
    for (int i = 0; i < n; ++i)
      longest[i][i] = 0;
    for (l = 2; l <= n; ++l)
      for (int i = 0; (i + l) <= n; ++i)
      {
        int m = INT_MIN;

        if ((s[i] == '(') && (s[i + l - 1] == ')'))
          m = max(m, longest[i + 1][i + l - 1 - 1] + 2);

        if ((s[i] == '[') && (s[i + l - 1] == ']'))
          m = max(m, longest[i + 1][i + l - 1 - 1] + 2);

        for (int j = 1; j < l; ++j)
          m = max(m, 
                  longest[i][i + j - 1] + longest[i + j][i + l - 1]);

        longest[i][i + l - 1] = m;
      }

    cout << longest[0][n - 1] << endl;
  }
  return 0;
}