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

#define int long long string s; stack sk; int Max;

signed main() { ios::sync_with_stdio(false); cin.tie(0);

if (!(cin >> s)) return 0;

sk.push(-1); 

for (int i = 0; i < s.size(); i++) {
    if (s[i] == '(' || s[i] == '[') {
        sk.push(i);
    } else {
        if (sk.size() > 1) { 
            char now = s[sk.top()];
            if ((now == '(' && s[i] == ')') || (now == '[' && s[i] == ']')) {
                sk.pop(); 
                Max = max(Max, i - sk.top()); 
            } else {
                while (!sk.empty()) sk.pop();
                sk.push(i);
            }
        } else {
            sk.pop();
            sk.push(i);
        }
    }
}

cout << Max << endl;
return 0;

}