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#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <set>

using namespace std;

const short int INF = 1000;
const short int MAXN = 200;

string s;
int dp[MAXN][MAXN];
string dp_data[MAXN][MAXN];

bool isOpening(char c) {
  return (c == '(' || c == '{' || c == '[') ? true : false;
}

short int type(char c) {
  if (c == '[' || c == ']') return 1;
  if (c == '{' || c == '}') return 2;
  if (c == '(' || c == ')') return 3;
  return -1;
}

bool compare(char c1, char c2) {
  return type(c1) == type(c2);
}

short int f(short int l, short int r) {
  if (l > r) return 0;
  if (dp[l][r] != -1) return dp[l][r];

  short int first_rule = (isOpening(s[l]) && !isOpening(s[r]) && compare(s[l], s[r])) ? f(l + 1, r - 1) : INF;
  short int second_rule = INF, index = 0;
  for (short int k = l; k < r; k++) {
    short int v = f(l, k) + f(k + 1, r);
    if (second_rule > v) {
      second_rule = v;
      index = k;
    }
  }
  if (first_rule < second_rule) {
    dp[l][r] = first_rule;
    string res = s[l] + dp_data[l + 1][r - 1] + s[r];
    dp_data[l][r] = res;
  } else {
    dp[l][r] = second_rule;
    string res = dp_data[l][index] + dp_data[index + 1][r];
    dp_data[l][r] = res;
  }
  return dp[l][r];
}

void init() {
  for (short int i = 0; i < MAXN; i++) {
    for (short int j = 0; j < MAXN; j++) {
      dp[i][j] = -1;
    }
  }
  for (short int i = 0; i < MAXN; i++) {
    dp[i][i] = 1;
  }
}

signed main() {
  cin >> s;
  init();
  short int minimum = f(0, s.size() - 1);
  cout << dp_data[0][s.size() - 1] << endl;
  return 0;
}