#include #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 int ui; const ll mod = (ll)(1e+9) + 7; const ll INF = (ll)1000000007 * 1000000007; typedef pair P; #define stop char nyaa;cin>>nyaa; #define rep(i,n) for(int i=0;i=0;i--) #define Rep(i,sta,n) for(int i=sta;i=1;i--) #define Rep1(i,sta,n) for(int i=sta;i<=n;i++) typedef long double ld; typedef complex Point; const ld eps = 1e-8; const ld pi = acos(-1.0); typedef pair LP; typedef pair LDP; int main() { ld n; cin >> n; cout << fixed << setprecision(1); cout << n * 3.5 << endl; return 0; }