#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string s;
  cin >> s;
  vector<long long> v1, v2, v3;
  int n = s.size();
  for (int i = 0; i < n; i++) {
    if (s[i] == '[') v1.push_back(i);
    if (s[i] == ']') v2.push_back(i);
  }
  if (v1.size() == 0 or v2.size() == 0) {
    cout << -1 << "\n";
    return 0;
  }
  int p = v1[0];
  int q = v2[v2.size() - 1];
  if (p > q) {
    cout << -1 << "\n";
    return 0;
  }
  for (int i = p + 1; i < q; i++) {
    if (s[i] == ':') v3.push_back(i);
  }
  if (v3.size() == 0) {
    cout << -1 << "\n";
    return 0;
  }
  int x = v3[0];
  int y = v3[v3.size() - 1];
  if (x == y) {
    cout << -1 << "\n";
    return 0;
  }
  int c = 0;
  for (int i = x + 1; i < y; i++) {
    if (s[i] == '|') c++;
  }
  cout << 4 + c << "\n";
}
