//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;
}