#include<bits/stdc++.h>
using namespace std;

typedef long long int           ll;
typedef unsigned long long int  ull;
typedef vector<int>             vi;
typedef vector<vi>              vvi;
typedef pair<int,int>           pii;
typedef vector< pii >           vpii;
typedef set<int>                sti;

#define pb                      push_back
#define pob                     pop_back
#define mp                      make_pair
#define ff                      first
#define ss                      second
#define loop1(i,n)              for(int i=1; i<=int(n); i++)
#define loop(i,y)               for(int i=0; i<int(y); i++)
#define rloop(i,y)              for(int i=int(y)-1; i>=0; i--)
#define read()                  freopen("input.txt", "r", stdin)
#define write()                 freopen("output.txt", "w", stdout)
#define cspf(i)                 printf("Case %d: ", i)
/// Constants
#define eps                     1e-9
#define PI                      acos(-1.0)  // 3.1415926535897932
char s[500009];
int main()
{
    scanf("%s",s);
    int i,ln,sz=0,sb=0,eb=0,fb=0,lb=0;
    ln=strlen(s);
    for(i=0;i<ln;i++){
        if(fb==0){
            if(s[i]=='['){
                sb=i;
                fb++;
            }
        }
        if(s[i]==']'){
            eb=i;
            lb++;
        }
    }
    if(sb+3>eb || fb==0 || lb==0){
        cout<<"-1"<<endl;
        return 0;
    }
    sz+=2;
    int c1=0,c2=0,fc=0,lc=0;
    for(i=sb+1;i<eb;i++){
        if(fc==0){
            if(s[i]==':'){
                c1=i;
                fc++;
                continue;
            }
        }
        if(s[i]==':'){
            c2=i;
            lc++;
        }
    }
    if(c1+1>c2 || fc==0 || lc==0){
        cout<<"-1"<<endl;
        return 0;
    }
    sz+=2;
    for(i=c1+1;i<c2;i++){
        if(s[i]=='|')
            sz++;
    }
    cout<<sz<<endl;
    return 0;
}