#include <bits/stdc++.h>
using namespace std;
int main() {
  int t = 1;
  while (t--) {
    string str;
    cin >> str;
    int b1 = -1, b2 = -1, s2 = -1, s1 = -1;
    for (long long int i = 0; i < str.length(); i++) {
      if (str[i] == '[') {
        b1 = i;
        break;
      }
    }
    if (b1 == -1) {
      cout << -1 << endl;
      continue;
    }
    for (long long int i = b1; i < str.length(); i++) {
      if (str[i] == ':') {
        s1 = i;
        break;
      }
    }
    if (s1 == -1) {
      cout << -1 << endl;
      continue;
    }
    for (int j = str.length() - 1; j > s1; j--) {
      if (str[j] == ']') {
        b2 = j;
        break;
      }
    }
    if (b2 == -1 || s1 > b2) {
      cout << -1 << endl;
      continue;
    }
    for (int j = b2; j > s1; j--) {
      if (str[j] == ':') {
        s2 = j;
        break;
      }
    }
    if (s2 == -1 || s1 > s2) {
      cout << -1 << endl;
      continue;
    }
    long long int ans = 4;
    for (long long int i = s1 + 1; i < s2; i++) {
      if (str[i] == '|') ans++;
    }
    cout << ans << endl;
  }
}
