//poj 2955

//sep9

#include <iostream>

using namespace std;

char s[128];

int dp[128][128];

int n;

int rec(int l,int r)

{

	if(dp[l][r]!=-1)

		return dp[l][r];

	if(l==r)

		return dp[l][r]=0;

	if(l+1==r){

		if(s[l]=='('&&s[r]==')')

			return dp[l][r]=2;

		if(s[l]=='['&&s[r]==']')

			return dp[l][r]=2;

	}

	int maxx=0;

	if(s[l]=='('&&s[r]==')')

		maxx=max(maxx,2+rec(l+1,r-1));

	if(s[l]=='['&&s[r]==']')

		maxx=max(maxx,2+rec(l+1,r-1));

	for(int k=l;k<=r-1;++k)

		maxx=max(maxx,rec(l,k)+rec(k+1,r));

	return dp[l][r]=maxx;

}

int main()

{

	while(scanf("%s",s)==1){

		if(s[0]=='e')

			break;

		memset(dp,-1,sizeof(dp));

		n=strlen(s);

		printf("%d\n",rec(0,n-1));

	}

	return 0;

}