#include<bits/stdc++.h>
using namespace std;

int dp[1010][1010];
char w[1010];

int cost(char l, char r){
    int val = 0;
    if(l == ')' || l == ']') val++;
    if(r == '(' || r == '[') val++;
    if(abs(l - r) > 2) val++;
    return val;
}

int recur(int l, int r){
    if(dp[l][r] != -1) return dp[l][r];
    if(r-l+1 == 2) return dp[l][r] = cost(w[l], w[r]);
    int Min = recur(l+1, r-1) + cost(w[l], w[r]);
    for(int i=l+1 ; i<r ; i+=2) Min = min(Min, recur(l, i) + recur(i+1, r));
    return dp[l][r] = Min;
}

int main(){
    scanf(" %s",w+1);
    int n = strlen(w+1);
    memset(dp, -1, sizeof dp);
    printf("%d\n",recur(1, n));
    return 0;
}