#include<bits/stdc++.h>
using namespace std;
char s[110];
int a[110], f[110][110];
int main()
{
	scanf("%s", s+1);
	int len = strlen(s+1);
	memset(a, 0, sizeof(a));
	for (int i=1; i<=len; i++)
		switch(s[i])
		{
			case '(':a[i] = 1;break;
			case '[':a[i] = 2;break;
			case ']':a[i] = 3;break;
			case ')':a[i] = 4;
		}
	memset(f, 0, sizeof(f));
	for (int i=1; i<=len; i++)f[i][i]=1;
	for (int l=2; l<=len; l++)
	{
		for (int i=1; i<=len-l+1; i++)
		{
			int j=l+i-1;
			f[i][j]=101;if(a[i] + a[j] == 5 && a[i] < a[j])f[i][j] = f[i+1][j-1];
			for (int k=i; k < j; k++)f[i][j] = min(f[i][j], f[i][k] + f[k+1][j]);
		}	
	}
	printf("%d", f[1][len]);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
char s[110];
int a[110],f[110][110];
int main()
{
	scanf("%s",s+1);
	int len =strlen(s+1);
	memset(a,0,sizeof(a));
	for (int i=1;i<=len;i++)
		switch(s[i])
		{
			case '(':a[i] = 1;break;
			case '[':a[i] = 2;break;
			case ']':a[i] = 3;break;
			case ')':a[i] = 4;
		}
	memset(f,0,sizeof(f));
	for (int i=1;i<=len;i++)f[i][i]=1;
	for (int l=2;l<=len;l++)
	{
		for (int i=1; i<=len-l+1;i++)
		{
			int j=l+i-1;
			f[i][j]=101;if(a[i]+a[j]==5 && a[i]<a[j])f[i][j]=f[i+1][j-1];
			for (int k=i;k<j; k++)f[i][j]=min(f[i][j],f[i][k] + f[k+1][j]);
		}	
	}
	printf("%d",f[1][len]);
	return 0;
}