#include <bits/stdc++.h>
#pragma GCC optimize(3)
#pragma GCC target("avx,sse2,sse3,sse4,mmx")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
using namespace std;
int bz, ez, bm, em, ans;
string str, rstr;
int main() {
  cin >> str;
  rstr = str;
  reverse(rstr.begin(), rstr.end());
  if (str.find('[') != string::npos)
    bz = str.find('[');
  else {
    cout << -1;
    return 0;
  };
  if (rstr.find(']') != string::npos)
    ez = rstr.find(']');
  else {
    cout << -1;
    return 0;
  };
  ez = str.size() - 1 - ez;
  if (bz > ez) {
    cout << -1;
    return 0;
  };
  str = str.substr(bz, ez - bz + 1);
  rstr = str;
  reverse(rstr.begin(), rstr.end());
  if (str.find(':') != string::npos)
    bm = str.find(':');
  else {
    cout << -1;
    return 0;
  };
  if (rstr.find(':') != string::npos)
    em = rstr.find(':');
  else {
    cout << -1;
    return 0;
  };
  em = str.size() - 1 - em;
  if (bm >= em) {
    cout << -1;
    return 0;
  };
  ans = 4;
  for (int i = bm + 1; i <= em - 1; i++)
    if (str[i] == '|') ans++;
  printf("%d", ans);
  return 0;
}
