#include <iostream>
using namespace std;

int dp[101][101];
int bk[101][101];
string s;

void rec(int l, int r){
    if (dp[l][r] == r - l + 1)
        return;
    if (dp[l][r] == 0){
        cout << s.substr(l, r - l + 1);
            return;
    }
    if (bk[l][r] == -1) {
        cout << s[l];
        rec(l + 1, r - 1);
        cout << s[r];
        return;
    }
    rec(l, bk[l][r]);
    rec(bk[l][r] + 1, r);
}



int main() {
    cin >> s;
    int n = s.size();
    for (int r = 0; r < n; ++r)
        for (int l = r; l >= 0; --l){
            if (l == r)
                dp[l][r] = 1;
            else{
                int best = 1000000; int mk = -1;
                if (s[l] == '(' && s[r] == ')' || s[l] == '[' && s[r] == ']' || s[l] == '{' && s[r] == '}')
                    best = dp[l + 1][r - 1];
                for (int k = l; k < r; ++k)
                    if (dp[l][k] + dp[k + 1][r] < best){
                        best = dp[l][k] + dp[k + 1][r];
                        mk = k;
                    }
                dp[l][r] = best; bk[l][r] = mk;
        }
}
    rec(0, n - 1);
    return 0;
}