#include #include #include #include #include #include #include #include #include typedef long double ld; typedef long long ll; const ll INF = (ll)1e18 + 1; const ll MOD = 1e9 + 7; // Split namespace util { std::vector< std::string > split(std::string s, char delimiter) { std::vector< std::string > vs; std::string sub; for (auto c : s) { if (c == delimiter) vs.push_back(sub), sub.clear(); else sub += c; } vs.push_back(sub); return vs; } } // namespace util // Minimum, Maximum template T minimum(T head, T tail) { return std::min(head, tail); } template H minimum(H head, T... tail) { return std::min(head, minimum(tail...)); } template T maximum(T head, T tail) { return std::max(head, tail); } template H maximum(H head, T... tail) { return std::max(head, maximum(tail...)); } // Output template std::ostream& operator << (std::ostream& os, std::pair p) { return os << p.first << " " << p.second; } template std::ostream& operator << (std::ostream& os, std::vector< T > v) { for (ll i = 0; i < (ll)v.size(); i++){ os << " [" << i << "]" << v[i]; if (i % 10 == 9) os << std::endl; } return os; } template std::ostream& operator << (std::ostream& os, std::vector< std::pair > vp) { ll i = 0; for (auto p : vp){os << " [" << i++ << "]" << p.first << " " << p.second; if (i % 10 == 0) os << std::endl;} return os; } void print(){ std::cout << std::endl; } template void print(H head) { std::cout << head << std::endl; } template void print(H head, T... tail){ std::cout << head << " ", print(tail...); } int main() { std::cin.tie(nullptr); std::ios::sync_with_stdio(false); ll T; std::cin >> T; std::vector< ll > vx(T+1, 0LL); for (ll i = 1; i <= T; i++) { std::cin >> vx[i]; } char judge = 'T'; for (ll i = 1; i < T; i++) { if (std::abs(vx[i]) > i+1 || std::abs(vx[i] - vx[i-1]) != 1) { judge = 'F'; } } print(judge); return 0; }