#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int id = -1, id1 = -1, id2, id3, cnt = 0, x;
  string st;
  cin >> st;
  for (long long int i = 0; i < st.length(); i++) {
    if (st[i] == '[') {
      id = i;
      break;
    }
  }
  for (long long int i = st.length() - 1; i >= 0; i--) {
    if (st[i] == ']') {
      id1 = i;
      break;
    }
  }
  if (id == -1 || id1 == -1) {
    cout << -1 << endl;
    return 0;
  }
  if (id > id1) {
    cout << -1 << endl;
    return 0;
  }
  id2 = st.length() + 3;
  for (long long int i = id + 1; i < id1; i++) {
    if (st[i] == ':') {
      id2 = min(id2, i);
      cnt++;
    }
    if (cnt == 2) break;
  }
  if (cnt < 2) {
    cout << -1 << endl;
    return 0;
  }
  id3 = -1;
  for (long long int i = id1 - 1; i > id2; i--) {
    if (st[i] == ':') {
      id3 = i;
      break;
    }
  }
  if (id3 == -1) {
    cout << -1 << endl;
    return 0;
  }
  x = 0;
  for (long long int i = id2 + 1; i < id3; i++) {
    if (st[i] == '|') x += 1;
  }
  cout << (4 + x) << endl;
  return 0;
}
