#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <set>
#include <utility>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>
#include <cstdio>
#include <map>
#include <list>

using namespace std;

typedef long long ll;
typedef pair<ll,ll> P;

#define _upgrade ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define rep(i,x) for(ll i = 0; i < (ll)(x); i++)
#define all(x) (x).begin(), (x).end()
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define pb push_back

template<class T1, class T2> void chmin(T1 &a, T2 b){if(a>b)a=b;}
template<class T1, class T2> void chmax(T1 &a, T2 b){if(a<b)a=b;}

//ll gcd(ll a, ll b){return b?gcd(b,a%b):a;}
//ll lcm(ll x, ll y) {return x / gcd(x, y) * y;}

int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};

const ll MOD = 1e9 + 7;
const ll INF = 1e9;
const long double PI = 3.14159265358979323846;


// ****************************************CODE***************************************//





int main(){
    int n;
    cin >> n;
    int tmp = n * 1.5;

    cout << tmp << endl;
}