#include<bits/stdc++.h>
using namespace std;
string s; 
int main(){
	cin>>s;
	string ans="[:";
	int l=-1,r=-1,l2=-1,r2=-1;
	for(register int i=0;i<=s.size()-1;i++){
		if(s[i]=='['&&l==-1){
			l=i;
		}
		if(s[i]==']'){
			r=i;
		}
	}
	if(r-l+1<=4||l==-1||r==-1){
		cout<<-1;
		return 0;
	}
	for(register int i=l;i<=r;i++){
		if(s[i]==':'){
			if(l2==-1){
				l2=i;
			}
			r2=i;
		}
	}
	if(l2==r2||l2==-1||r2==-1){
		cout<<-1;
		return 0;
	}
	for(register int i=l2+1;i<=r2-1;i++){
		if(s[i]=='|'){
			ans=ans+'|';
		}
	}
	ans=ans+":]";
	cout<<ans.size();
    return 0;
}

https://www.luogu.com.cn/record/136158922