dfs

#include<bits/stdc++.h>
using namespace std;
#define endl "\n"
string s;
int dp[105][105];
bool check(char a,char b)
{
	if(a=='('&&b==')'||a=='['&&b==']')
		return true;
	return false;
}
int dfs(int l,int r)
{
	if(l>r)
		return 0;		
	if(dp[l][r])
		return dp[l][r];		
	if(l==r)
		return dp[l][r]=1;
	dp[l][r]=100;
	for(int i=l;i<r;i++)
		dp[l][r]=min(dp[l][r],dfs(l,i)+dfs(i+1,r));
	if(check(s[l],s[r]))
		dp[l][r]=min(dp[l][r],dfs(l+1,r-1));	
	return dp[l][r];
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>s;
	s=" "+s;
	cout<<dfs(1,s.size()-1)<<endl;
	return 0;
}