#include <bits/stdc++.h>
using namespace std;
long long int mod = 1000000007;
bool check(pair<long long int, long long int> p1,
           pair<long long int, long long int> p2) {
  return p2.second > p1.second;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string s;
  cin >> s;
  bool check = false;
  long long int l1 = -1, r1 = -2;
  for (int i = 0; i < s.size(); i++) {
    if (!check) {
      if (s[i] == '[') check = true;
    } else if (check) {
      if (s[i] == ':') {
        l1 = i;
        break;
      }
    }
  }
  check = false;
  for (int i = s.size() - 1; i >= 0; i--) {
    if (!check) {
      if (s[i] == ']') {
        check = true;
      }
    } else if (check) {
      if (s[i] == ':') {
        r1 = i;
        break;
      }
    }
  }
  if (l1 >= r1 || l1 == -1 || r1 == -2) {
    cout << -1;
    return 0;
  }
  long long int ans = 0;
  for (int i = l1; i < r1; i++) {
    if (s[i] == '|') {
      ans++;
    }
  }
  cout << ans + 4;
  return 0;
}
