#include <bits/stdc++.h>
#define rep(i,a,b) for(int i = (a); i <= (b); i++)
#define rng(a) a.begin(), a.end()
#define sz(x) (int)(x).size()
#define se second
#define fi first
#define prev            :oyhhhhhhyo:    
#define next         .sdNNNmNNNNNNNmds. 
#define y0          -hNNNNy`yNNNNNN`/Nh-
#define y1          mNNNNNd+dNNNNNN+sNNm
#define yn          mNNNNNNNNy--:smNNNms
#define tm          .+oooooosyysooooo+- 
#define read               :yhy/        
#define rank              :mNmo         
#define index              ... 
#define pb push_back
#define pcnt __builtin_popcountll
#define rrep(i,a,b) for(int i = (b); i >= (a); i--)
#ifdef LOCAL
#define rall(x,a) for(x : a)
#define LL "%lld"
#else
#define rall(x,a) for(auto x : a)
#define LL "%I64d"
#endif
#define PI 3.14159265358979323846
#define MOD 1000000007
#define endl "\n"
typedef long long ll;
using namespace std;

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    int m = n + n / 2;
    cout << m << endl;
    return 0;
}