#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;
inline void smax(int &x, int y) { x = max(x, y); }
inline void smin(int &x, int y) { x = min(x, y); }
ll gcd(ll a, ll b) { return ((b == 0) ? a : gcd(b, a % b)); }
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  string s;
  cin >> s;
  int n = s.size();
  int st = -1, en = -1;
  int f = 0;
  for (__typeof(n) i = (0) - ((0) > (n)); i != (n) - ((0) > (n));
       i += 1 - 2 * ((0) > (n))) {
    if (s[i] == '[' && st == -1) {
      f = 1;
      st = i;
    }
    if (s[i] == ':' && f == 1) {
      st = i;
      break;
    }
  }
  f = 0;
  for (int i = n - 1; i >= 0; i--) {
    if (s[i] == ']' && en == -1) {
      en = i;
      f = 1;
    }
    if (f == 1 && s[i] == ':') {
      en = i;
      break;
    }
  }
  if (st == -1 || en == -1) {
    cout << -1 << endl;
    exit(0);
  }
  if (s[st] == '[' || s[en] == ']' || st >= en) {
    cout << -1 << endl;
    exit(0);
  }
  int cnt = 0;
  for (__typeof(en) i = (st + 1) - ((st + 1) > (en));
       i != (en) - ((st + 1) > (en)); i += 1 - 2 * ((st + 1) > (en))) {
    if (s[i] == '|') cnt++;
  }
  cout << cnt + 4;
}
