#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

const int MAX_LENGTH = 100;
const int INFINITY = 1000000;

string buffer;
int bestlen[MAX_LENGTH][MAX_LENGTH];

bool match (char c, char d){
  return (c == '(' && d == ')') || (c == '[' && d == ']');
}

int main (){
  
  while (true){
    cin >> buffer;
    if (buffer == "end") break;
    
    int L = buffer.length();
    
    // clear out buffer    
    for (int i = 0; i < MAX_LENGTH; i++)
      for (int j = 0; j < MAX_LENGTH; j++)
	bestlen[i][j] = 0;
    
    // dynamic programming
    for (int len = 2; len <= L; len++){
      
      // find length of longest regular brackets subsequence
      // contained within s = buffer[i]...buffer[j]
      for (int i = 0; i + len - 1 < L; i++){
	int j = i + len - 1;

	// look for all possible ways of building s from
	// either two smaller regular brackets subsequences
	// or from a regular brackets subsequence + "junk"
	for (int k = i; k < j; k++){
	  if (bestlen[i][j] < bestlen[i][k] + bestlen[k+1][j])
	    bestlen[i][j] = bestlen[i][k] + bestlen[k+1][j];
	}

	// consider s of the form (s') or [s']
	if (match (buffer[i], buffer[j])){
	  if (bestlen[i][j] < bestlen[i+1][j-1]+2)
	    bestlen[i][j] = bestlen[i+1][j-1]+2;
	}
      }
    }

    cout << bestlen[0][L-1] << endl;
  }

  return 0;
}