#include <bits/stdc++.h>
#define int long long

using namespace std;

int dp[105][105];
int ep[105][105];

char f(char c) {
      if (c == '(') return ')';
      if (c == ')') return '(';
      if (c == '{') return '}';
      if (c == '}') return '{';
      if (c == '[') return ']';
      if (c == ']') return '[';
}


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 (ep[l][r] == -1) {
            cout << s[l];
            rec(l + 1, r - 1);
            cout << s[r];
            return;
      }
      rec(l, ep[l][r]);
      rec(ep[l][r] + 1, r);
}

signed 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; ep[l][r] = mk;
                  }
            }


      rec(0, n - 1);

      return 0;
}