#define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair i_i; typedef pair ll_i; typedef pair d_i; typedef pair ll_ll; typedef pair d_d; struct edge { int u, v; double w; }; ll MOD = 1000000007; ll _MOD = 1000000009; double EPS = 1e-10; int main() { int N; cin >> N; cout << N * 3.5 << endl; }