#include <bits/stdc++.h>
using namespace std;
const int maxn = 500500;
char s[maxn];
signed main() {
  while (~scanf("%s", s)) {
    int lo = -1, hi = -1, ok = 0;
    for (int i = 0; s[i]; i++) {
      if (s[i] == '[') ok = 1;
      if (s[i] == ':' && ok) {
        lo = i;
        break;
      }
    }
    int n = strlen(s);
    ok = 0;
    for (int i = n - 1; i >= 0; i--) {
      if (s[i] == ']') ok = 1;
      if (s[i] == ':' && ok) {
        hi = i;
        break;
      }
    }
    if (lo == -1 || hi == -1 || lo >= hi) {
      printf("-1\n");
      continue;
    }
    int ret = 0;
    for (int i = lo + 1; i < hi; i++) {
      if (s[i] == '|') ret++;
    }
    printf("%d\n", ret + 4);
  }
  return 0;
}
