#include<iostream>

#include<cstdio>

#include<cstring>

using namespace std;

char c[105];

int f[105][105];

bool p(char x,char y)

{

	if((x=='('&&y==')')||(x=='['&&y==']'))return true;

	else return false;

}

int main()

{

	while(1)

	{

		gets(c);

		if(c[0]=='e')return 0;

		memset(f,0,sizeof f);

		int len=strlen(c);

		for(int i=len-1;i>=0;i--)

			for(int j=i+1;j<len;j++)

			{

				for(int k=i;k<=j-1;k++)

					f[i][j]=max(f[i][j],f[i][k]+f[k+1][j]);//+

				if(p(c[i],c[j]))

					f[i][j]=max(f[i][j],f[i+1][j-1]+2);

//				printf("%d-%d:%d\n",i,j,f[i][j]);

			}

		printf("%d\n",f[0][len-1]);

	}

}