#include <bits/stdc++.h>
using namespace std;
int main() {
  string str1;
  int ln, i, j, ck1 = 0, ck2 = 0, ck3 = 0, ck4 = 0, ck = 0, k, a = 0, x, y;
  cin >> str1;
  ln = str1.size();
  char str2[ln + 2];
  if (ln < 4) {
    cout << "-1" << endl;
    return 0;
  }
  for (i = 0, j = 0, k = ln - 1; i < ln; i++, k--) {
    if (str1[i] == '[' && ck1 == 0) {
      ck1 = 1;
      str2[j++] = str1[i];
    } else if (str1[i] == ':' && ck1 == 1 && ck2 == 0) {
      ck2 = 1;
      str2[j++] = str1[i];
      x = (ln - i) - 1;
    } else if (ck2 == 1) {
      str2[j++] = str1[i];
    }
  }
  str2[j] = '\0';
  if (ck1 == 1 && ck2 == 1) {
    string str3(str2);
    reverse(str3.begin(), str3.end());
    for (i = 0, k = 0; i < j; i++) {
      if (str3[i] == ']' && ck4 == 0) {
        ck4 = 1;
      } else if (str3[i] == ':' && ck4 == 1 && ck3 == 0 && i != x) {
        ck3 = 1;
      } else if (ck3 == 1 && str3[i] == '|') {
        a++;
      }
    }
    if (ck4 == 1 && ck3 == 1) {
      cout << 4 + a << endl;
    } else
      cout << "-1" << endl;
  } else {
    cout << "-1" << endl;
  }
  return 0;
}
