import java.util.*;
import java.io.*;
public class brackets {
    public static void main(String args[]) {
	try {
	    BufferedReader br=new BufferedReader(new
						 InputStreamReader(System.in));
	    while(true) {
		String cur=br.readLine();
		if(cur.equals("end")) break;
		
		int n=cur.length();
		char str[]=new char[cur.length()];
		for(int i=0;i<n;i++) str[i]=cur.charAt(i);

		int m[][]=new int[n][n+1];
		for(int len=2;len<=n;len++) {
		    for(int i=0;i<n-len+1;i++) {
			int best=0;
			if((str[i]=='(' && str[i+len-1] ==')') ||
			   (str[i]=='[' && str[i+len-1] ==']')) {
			    best=2+m[i+1][len-2];
			}
			//now check concat
			for(int j=i+1;j<=i+len-1;j++) {
			    int temp=m[i][j-i]+m[j][i+len-j];
			    if(temp>best) best=temp;
			}
			m[i][len]=best;
		    }
		}
		System.out.println(m[0][n]);
	    }
	}catch(Exception e) {
	    e.printStackTrace();
	}
    }
}