#include <bits/stdc++.h>
using namespace std;
int64_t start = -1;
int64_t ended = -1;
int64_t colonstart;
int64_t colonend;
bool check(string temp) {
  for (int64_t x = 0; temp[x] != '\0'; x++) {
    if (temp[x] == '[') {
      start = x;
      break;
    }
  }
  for (int64_t x = start + 1; temp[x] != '\0'; x++) {
    if (temp[x] == ']') {
      ended = x;
    }
  }
  if (start != -1 && ended != -1) {
    int64_t count = 0;
    for (int64_t x = start; x <= ended; x++) {
      if (temp[x] == ':') count += 1;
    }
    if (count >= 2) {
      for (int64_t x = start; x <= ended; x++) {
        if (temp[x] == ':') {
          colonstart = x;
          break;
        }
      }
      for (int64_t x = start; x <= ended; x++) {
        if (temp[x] == ':') {
          colonend = x;
        }
      }
    } else {
      return false;
    }
  } else {
    return false;
  }
}
int main() {
  string temp;
  cin >> temp;
  int64_t length = 0;
  for (length = 0; temp[length] != '\0'; length++) {
  }
  if (check(temp)) {
    int64_t removedlength = 0;
    removedlength += (colonstart - start - 1);
    removedlength += (ended - colonend - 1);
    removedlength += (start);
    removedlength += (length - 1 - ended);
    for (int64_t x = colonstart + 1; x <= colonend - 1; x++) {
      if (temp[x] != '|') removedlength += 1;
    }
    cout << length - removedlength << endl;
  } else {
    cout << -1 << endl;
  }
}
