#include <bits/stdc++.h>
using namespace std;
int main() {
  long long flag = 0;
  long long maxsize = -1, t1 = -1, t2 = -1;
  string s;
  getline(cin, s);
  long long m = s.size();
  for (long long i = 0; i < m; i++) {
    if (s[i] == '[') {
      for (i = i + 1; i < m; i++) {
        if (s[i] == ':') {
          t1 = i;
          flag = 1;
          break;
        }
      }
    }
    if (flag) break;
  }
  flag = 0;
  for (long long i = m - 1; i >= 0; i--) {
    if (s[i] == ']') {
      for (i = i - 1; i >= 0; i--) {
        if (s[i] == ':') {
          t2 = i;
          flag = 1;
          break;
        }
      }
    }
    if (flag) break;
  }
  if (t1 < t2 && t1 > 0 && t2 > 0) {
    maxsize = 4;
    for (long long i = t1 + 1; i < t2; i++) {
      if (s[i] == '|') maxsize++;
    }
  }
  cout << maxsize;
}
