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

int main(){
    string s;cin>>s;
    stack<char> q;
    for(auto i:s){
        if(i=='>'){
            while(!q.empty()&&q.top()=='t')q.pop();
            if(!q.empty()&&q.top()=='s')q.pop();
            else q.push('>');
        }else if(i=='='){
            if(!q.empty()&&(q.top()=='<')){
                q.top()='s';
                q.push('t');
            }else if(!q.empty()&&(q.top()=='t'))q.push('t');
            else q.push('=');
        }else{
            q.push('<');
        }
    }
    cout<<q.size()<<"\n";
}