#include <bits/stdc++.h>
using namespace std;
const int INF = (int)2e9;
const long long INFL = (long long)9e18;
const int MAXINT = ((~0) ^ (1 << 31));
const long long MAXLL = ((~0) ^ ((long long)1 << 63));
template <class T>
inline T pow2(T a) {
  return a * a;
}
template <class T>
inline bool mineq(T& a, T b) {
  return (a > b) ? (a = b, true) : false;
}
template <class T>
inline bool maxeq(T& a, T b) {
  return (a < b) ? (a = b, true) : false;
}
const int maxn = 1e6;
long long l, r, cnt, flg1, flg2;
string s;
int main() {
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == '[') flg1 = 1;
    if (s[i] == ':' && flg1) {
      l = i;
      break;
    }
  }
  for (int i = s.size() - 1; i >= 0; i--) {
    if (s[i] == ']') flg2 = 1;
    if (s[i] == ':' && flg2) {
      r = i;
      break;
    }
  }
  if (l < r && flg1 && flg2 && l && r) {
    for (int i = l + 1; i < r; i++) {
      if (s[i] == '|') {
        cnt++;
      }
    }
    cout << cnt + 4;
  } else
    cout << -1;
}
