#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 main(){
    scanf(" %s",w+1);
    int n = strlen(w+1);
    for(int i=1 ; i<n ; i++) dp[i][i+1] = cost(w[i], w[i+1]);
    for(int sz=4 ; sz<=n ; sz+=2){
        for(int i=1 ; i<=n ; i++){
            int j=i+sz-1;
            if(j > n) break ;
            dp[i][j] = dp[i+1][j-1] + cost(w[i], w[j]);
            for(int k=i+1 ; k<j ; k+=2){
                dp[i][j] = min(dp[i][j], dp[i][k] + dp[k+1][j]);
            }
        }
    }
    printf("%d\n",dp[1][n]);
    return 0;
}