#include<bits/stdc++.h>
#define rep(i,n) for(int i = 0;i < (int)n;i++)
#define repb(i,n) for(int i = (int)n;i >= 0;i--)
#define reps(i,m,n) for(int i = (int)m;i < (int)n;i++)
#define repsb(i,m,n) for(int i = (int)m;i >= (int)n;i--)
#define SORT(v,n) sort(v,v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define pb(a) push_back(a)
#define INF 999999999999999999
#define ll long long int
int dy[]={0, 0, 1, -1, 0};
int dx[]={1, -1, 0, 0, 0};
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1;} return 0;}
//vector<vector<int>> vec(n_rows, vector<int>(n_cols, value));
using namespace std;
int main(int argc, char const *argv[]) {
    int n;
    cin>>n;
    cout << (double)n / 2;
    return 0;
}