#include // clang-format off using namespace std; #define all(a) a.begin(), a.end() #define int long long #define over_load_(_1, _2, _3, _4, NAME, ...) NAME #define rep(...) over_load_(__VA_ARGS__, rep4, rep3, rep2)(__VA_ARGS__) #define rep2(i, r) for (int i = 0; i < static_cast(r); (i) += 1) #define rep3(i, l, r) for (int i = static_cast(l); i < static_cast(r); (i) += 1) #define rep4(i, l, r, stride) for (int i = static_cast(l); i < static_cast(r); (i) += (stride)) #define rrep(...) over_load_(__VA_ARGS__, rrep4, rrep3, rrep2)(__VA_ARGS__) #define rrep2(i, r) for (int i = static_cast(r) - 1; i >= 0; (i) -= 1) #define rrep3(i, l, r) for (int i = static_cast(r) - 1; i >= static_cast(l); (i) -= 1) #define rrep4(i, l, r, stride) for (int i = static_cast(r) - 1; i >= static_cast(l); (i) -= (stride)) #define fore(i, a) for (auto &i : a) template inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); } template inline bool chmin(T1 &a, T2 b) { return a > b and (a = b, true); } constexpr char newl = '\n'; long long pow2(int x) {return x * x;} bool isupper(char c) {return ('A' <= c and c <= 'Z');} bool islower(char c) {return ('a' <= c and c <= 'z');} bool isnumber(char c) {return ('0' <= c and c <= '9');} // O(logX) int getdigit(long long x) { int res = 0; while(x > 0) { res++; x /= 10; } return res; } using ll = long long; using vi = vector; using vll = vector; using vvi = vector; using vvll = vector; using vp = vector>; using vs = vector; const ll sup = LONG_LONG_MAX / 2 - 1; const double pi = 3.141592653589793; int n; long double solve() { return 3.5 * n; } signed main() { cin >> n; cout << fixed << setprecision(3); cout << solve() << newl; }