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

#define ll long long
#define f(i,a,b) for(ll i=a;i<b;i++)
#define fd(i,a,b) for(ll i=a;i>=b;i--)
#define rep(it,a) for(auto it: a)
#define pb emplace_back
#define mp make_pair
#define vll vector<ll>
#define pll pair<ll,ll>
#define MOD (1000LL*1000*1000+7)
#define INF (MOD*MOD)
#define F first
#define S second
#define all(a) a.begin(),a.end()
#define tri pair<ll,pll>
#define vpll vector<pll>
#define vvll vector<vll>
#define LL(t) ll t;cin>>t
#define VLL(v,n) vll v(n);f(i,0,n){cin>>v[i];}

ll power(ll a, ll b, ll mod) { // return (a^b)%mod
    if(b==0) return 1;
    ll half=power(a,b / 2,mod);
    ll full=(half*half)%mod;
    return (b%2) ? (a*full)%mod : full;
}

ll divMod(ll a, ll b, ll mod){ // return (a/b) % mod , works iff a%b=0
    return ((a%mod)*(power(b, MOD-2, MOD)))%mod;
}

bool comp(tri & a, tri &b){
    if(a.first!=b.first)
        return a.first < b.first;
    else{
        if(a.S.F!=b.S.F)
            return a.S.F < b.S.F;
        else
            return a.S.S < b.S.S;
    }
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    ll a,b;
    cin>>a>>b;
    if (a % 2) {
        cout << a / 2 << ".5" << endl;
    } else {
        cout << a / 2 << endl;
    }
    return 0;
}