#include <bits/stdc++.h>
using namespace std;
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
void solve() {
  string s;
  cin >> s;
  long long cnt = 0;
  while (true) {
    if (s[0] == '[')
      break;
    else
      s.erase(0, 1);
    if (s.length() == 0) {
      cout << "-1"
           << "\n";
      return;
    }
  }
  while (true) {
    if (s[s.length() - 1] == ']')
      break;
    else
      s.erase(s.length() - 1, 1);
    if (s.length() == 0) {
      cout << "-1"
           << "\n";
      return;
    }
  }
  while (true) {
    if (s.size() >= 2 && s[1] == ':')
      break;
    else if (s.size() >= 2)
      s.erase(1, 1);
    if (s.size() == 1) {
      cout << "-1"
           << "\n";
      return;
    }
  }
  while (true) {
    if (s.size() > 3 && s[s.length() - 2] == ':')
      break;
    else if (s.size() >= 2)
      s.erase(s.length() - 2, 1);
    if (s.size() <= 3) {
      cout << "-1"
           << "\n";
      return;
    }
  }
  for (int i = 2; i < s.length() - 2; i++) {
    if (s[i] != '|') cnt++;
  }
  cout << s.size() - cnt << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
}
