#ifdef EVAL
#include "grader.h"
#include "encoder.h"
#endif
#include <bits/stdc++.h>
using namespace std;
namespace changes{
#define Bit(x, i) ((x) >> (i) & 1)
#define Mask(i) (1 << (i))
const int block3 = 39;
const int block2 = 62;
const int LG = 10;
long long p2[block2], p3[block3];
void init(){
p2[0] = 1;
for (int i = 1; i < block2; ++ i)
p2[i] = p2[i - 1] * 2;
p3[0] = 1;
for (int i = 1; i < block3; ++ i)
p3[i] = p3[i - 1] * 3;
}
long long fval3(vector <int> states){
long long rt = 0;
for (int i = 0; i < int(states.size()); ++ i)
rt += p3[i] * states[i];
return rt;
}
vector <int> tval3(long long val, int num){
vector <int> states(num);
for (int i = 0; i < num; ++ i){
states[i] = val % 3;
val /= 3;
}
return states;
}
long long fval2(vector <int> states){
long long rt = 0;
for (int i = 0; i < int(states.size()); ++ i)
rt += p2[i] * states[i];
return rt;
}
vector <int> tval2(long long val, int num){
vector <int> states(num);
for (int i = 0; i < num; ++ i){
states[i] = val % 2;
val /= 2;
}
return states;
}
}
using namespace changes;
#ifndef EVAL
void encode_bit(int b){
}
#endif
void encode(int nv, int nh, int ne, int *v1, int *v2){
vector <vector <int>> adj(nv);
for (int i = 0; i < ne; ++ i){
adj[v1[i]].push_back(v2[i]);
adj[v2[i]].push_back(v1[i]);
}
vector <int> fa(nv, -1);
function <void(int)> dfs = [&](int u){
for (int v : adj[u]) if (v != fa[u] && v && fa[v] == -1){
fa[v] = u;
dfs(v);
}
};
dfs(0);
for (int i = 1; i < nv; ++ i){
for (int l = 0; l < LG; ++ l)
encode_bit(Bit(fa[i], l));
}
for (int r = 0; r < nh; ++ r){
vector <int> dist(nv, -1);
dist[r] = 0;
queue <int> qu;
qu.push(r);
while (qu.size()){
int u = qu.front(); qu.pop();
for (int v : adj[u]) if (dist[v] < 0){
dist[v] = dist[u] + 1;
qu.push(v);
}
}
for (int i = 1; i < nv; i += block3){
vector <int> tmp;
for (int j = i; j < min(nv, i + block3); ++ j)
tmp.push_back(dist[i] - dist[fa[i]] + 1);
for (int b : tval2(fval3(tmp), block2)) encode_bit(b);
}
}
}
#ifndef EVAL
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
cout << n / 2;
return 0;
}
#endif
#ifdef EVAL
#include "grader.h"
#include "decoder.h"
#endif
#include <bits/stdc++.h>
using namespace std;
namespace changes{
#define Bit(x, i) ((x) >> (i) & 1)
#define Mask(i) (1 << (i))
const int block3 = 39;
const int block2 = 62;
const int LG = 10;
long long p2[block2], p3[block3];
void init(){
p2[0] = 1;
for (int i = 1; i < block2; ++ i)
p2[i] = p2[i - 1] * 2;
p3[0] = 1;
for (int i = 1; i < block3; ++ i)
p3[i] = p3[i - 1] * 3;
}
long long fval3(vector <int> states){
long long rt = 0;
for (int i = 0; i < int(states.size()); ++ i)
rt += p3[i] * states[i];
return rt;
}
vector <int> tval3(long long val, int num){
vector <int> states(num);
for (int i = 0; i < num; ++ i){
states[i] = val % 3;
val /= 3;
}
return states;
}
long long fval2(vector <int> states){
long long rt = 0;
for (int i = 0; i < int(states.size()); ++ i)
rt += p2[i] * states[i];
return rt;
}
vector <int> tval2(long long val, int num){
vector <int> states(num);
for (int i = 0; i < num; ++ i){
states[i] = val % 2;
val /= 2;
}
return states;
}
}
using namespace changes;
#ifndef EVAL
int decode_bit(){
return 0;
}
void hops(int h, int c, int d){
}
#endif
void decode(int nv, int nh){
vector <int> fa(nv, -1);
vector <vector <int>> adj(nv);
for (int i = 1; i < nv; ++ i){
fa[i] = 0;
for (int l = 0; l < LG; ++ l)
if (decode_bit()) fa[i] |= Mask(l);
adj[fa[i]].push_back(i);
}
for (int r = 0; r < nh; ++ r){
vector <int> diff(nv);
for (int i = 1; i < nv; i += block3){
vector <int> tmp;
for (int j = 0; j < block2; ++ j)
tmp.push_back(decode_bit());
vector <int> cur = tval3(fval2(tmp), min(block3, nv - i));
for (int j = 0; j < min(block3, nv - i); ++ j)
diff[i + j] = cur[j] - 1;
}
vector <int> dist(nv);
dist[0] = 0; int u = r;
while (u){
dist[0] -= diff[u];
u = fa[u];
}
function <void(int)> dfs = [&](int u) {
for (int v : adj[u]) {
dist[v] = dist[u] + diff[v];
dfs(v);
}
};
dfs(0);
for (int i = 0; i < nv; ++ i)
hops(r, i, dist[i]);
}
}
#ifndef EVAL
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
cout << n / 2;
return 0;
}
#endif
