#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
const int N = 2e5 + 5;
const long long inf = 2e18;
const long long M = 1e9 + 7;
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  int ans = 0, l = -1, r = -1;
  for (int i = 0; i < s.size(); i++)
    if (s[i] == '[') {
      if (l == -1) l = i;
    } else if (s[i] == ']')
      r = i;
  if (l == -1 || r == -1 || r < l) {
    cout << -1;
    return 0;
  }
  int l1 = -1, r1 = -1;
  for (int i = l + 1; i < r; i++)
    if (s[i] == ':') {
      r1 = i;
      if (l1 == -1) l1 = i;
    }
  if (l1 == r1) {
    cout << -1;
    return 0;
  }
  ans = l + l1 - l - 1 + r - r1 - 1 + s.size() - r - 1;
  for (int i = l1 + 1; i < r1; i++)
    if (s[i] != '|') ans++;
  cout << s.size() - ans;
  return 0;
}
