#include <bits/stdc++.h>
using namespace std;
const int INF = 2000000009;
const int MX = 100005;
const double EPS = 1e-9;
const int MOD = 1000000007;
template <class T>
T gcd(T a, T b) {
  return (b != 0 ? gcd<T>(b, a % b) : a);
}
template <class T>
T lcm(T a, T b) {
  return (a / gcd<T>(a, b) * b);
}
template <class T>
inline bool read(T &x) {
  int c = getchar();
  int sgn = 1;
  while (~c && c < '0' || c > '9') {
    if (c == '-') sgn = -1;
    c = getchar();
  }
  for (x = 0; ~c && '0' <= c && c <= '9'; c = getchar()) x = x * 10 + c - '0';
  x *= sgn;
  return ~c;
}
int main() {
  string s;
  cin >> s;
  int len = s.length();
  int b1 = -1, b2 = -1, col1 = -1, col2 = -1, cnt = 0;
  for (int i = 0; i < len; i++) {
    if (b1 != -1 && col1 != -1) break;
    if (s[i] == '[')
      b1 = i;
    else if (s[i] == ':' && b1 != -1)
      col1 = i;
  }
  for (int i = (len - 1); i >= (0); i--) {
    if (col2 != -1 && b2 != -1) break;
    if (s[i] == ']')
      b2 = i;
    else if (s[i] == ':' && b2 != -1)
      col2 = i;
  }
  if (col2 != -1 && b2 != -1 && b1 != -1 && col1 != -1 && b1 < col1 &&
      col1 < col2 && col2 < b2) {
    for (int i = (col1 + 1); i <= (col2 - 1); i++)
      if (s[i] == '|') cnt++;
    cout << cnt + 4 << '\n';
  } else
    cout << -1 << '\n';
  return 0;
}
