#include <bits/stdc++.h>
using namespace std;
 
int main()
{
    int c = 0, d = 0, n;
    cin >> n;
    while (n--) {
        string s;
        cin >> s;
        if (s == "for") {
            ++d;
            c = max(c, d);
        } else if (s == "end") {
            --d;
        }
    }
    if (c == 0) {
        cout << "O(1)" << endl;
    } else if (c == 1) {
        cout << "O(n)" << endl;
    } else {
        cout << "O(n^" << c << ")" << endl;
    }
    return 0;
}

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18
instruction
for
for
instruction
end
for
instruction
instruction
instruction
for
instruction
instruction
end
instruction
end
end
instruction
instruction