#include "bits/stdc++.h"
using namespace std;

using ll = long long;
int INF = numeric_limits<int>::max() / 2;
ll LINF = numeric_limits<ll>::max() / 2;
int MOD = 1e9 + 7;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n;
    cin >> n;
    cout << n * 15 / 10 << endl;
    
}