ABC418B.cpp

#include <bits/stdc++.h>

using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vd = std::vector<double>;
using vvd = std::vector<vd>;

#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define RANGE_CIN(a) for (auto& x : a) std::cin >> x;
#define CHMAX(x,y) x = std::max(x,y)
#define CHMIN(x,y) x = std::min(x,y)
#define UNIQUE_ERASE(v) v.erase(std::unique(ALL(v)), v.end());
#define F_DIG_NUM(a) std::fixed << std::setprecision(a)
#define REP(i, n) for (ll i = 0; i < (ll)(n); i++)
#define REPR(i,n) for(ll i = (ll)(n); i >= 0; i--)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define EB(x) emplace_back(x)
#define EM(x) emplace(x)
#define PSORT(v, fs) std::sort(ALL(v), [](const auto& a, const auto& b) { return a.fs < b.fs; })
#define PRSORT(v, fs) std::sort(RALL(v), [](const auto& a, const auto& b) { return a.fs < b.fs; })

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);
    std::string s = "";
    std::cin >> s;
    double max = 0;
    ll count = 0;
    vll tpos;
    REP(i, s.size()) {
        if (s.at(i) == 't') {
            count++;
            tpos.EB(i);
        }
    }
    REP(i, tpos.size()) {
        REP(j, tpos.size()) {
            if (i >= j) continue;
            ll x = j - i + 1;
            ll t = tpos.at(j) - tpos.at(i) + 1;
            if (t < 3) continue;
            CHMAX(max, static_cast<double>(x - 2) / static_cast<double>(t - 2));
        }
    }
    if (count <= 1) {
        std::cout << 0 << std::endl;
        return 0;
    }
    std::cout << F_DIG_NUM(16) << max << std::endl;
    return 0;
}