#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  long long l = s.size();
  long long s1 = -1, s2 = -1, e1 = -1, e2 = -1;
  for (long long i = 0; i < l; i++) {
    if (s[i] == '[') {
      s1 = i;
      break;
    }
  }
  if (s1 == -1) {
    cout << "-1";
    return 0;
  }
  for (long long i = s1; i < l; i++) {
    if (s[i] == ':') {
      s2 = i;
      break;
    }
  }
  if (s2 == -1) {
    cout << "-1";
    return 0;
  }
  for (long long i = l - 1; i >= 0; i--) {
    if (s[i] == ']') {
      e1 = i;
      break;
    }
  }
  if (e1 == -1) {
    cout << "-1";
    return 0;
  }
  for (long long i = e1; i >= 0; i--) {
    if (s[i] == ':') {
      e2 = i;
      break;
    }
  }
  if (e2 == -1) {
    cout << "-1";
    return 0;
  }
  if (s2 < e2) {
    long long ct = 0;
    for (long long i = s2; i < e2; i++) {
      if (s[i] == '|') {
        ct++;
      }
    }
    cout << 4 + ct;
  } else {
    cout << "-1";
    return 0;
  }
}
