#include <iostream>
#include <cstring>
#include <vector>
#include <set>
#include <list>
#include <map>
#include <deque>
#include <algorithm>
#include <utility>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
#define for1(i,n) for (ll i=0;i<(n);i++)
#define for2(i,m,n) for (ll i=(m);i<(n);i++)
#define for3(i,m,n,d) for (ll i=(m);i<(n);i+=(d))
#define DEBUG 0
template <class T>
void dumplist(T list)
{
    for (auto item : list) {
        cout << item << " ";
    }
    cout << endl;
}



void solve()
{
    ll N;
    cin >> N;
    N *= 1.5;

    cout << N << endl;
}

int main()
{
    do {
        solve();
    } while (DEBUG);
}