Go: package main

import (
	"fmt"
	"bufio"
	"os"
	"strconv"
	"strings"
)

var sc = bufio.NewScanner(os.Stdin)

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

func nextLineInt() []int {
	arr := strings.Split(nextLine(), " ")
	var ret []int
	for _, v := range arr {
		x, _ := strconv.Atoi(v)
		ret = append(ret, x)
	}
	return ret
}

func main() {
	cin := nextLineInt()
	F := cin[0]
	fmt.Println((F-30)/2)
}

C++: #include <stdio.h>

int main(void) {
  int f;
  scanf("%d", &f);
  printf("%d\n", (f - 30) / 2);
  return 0;
}

C++: #include<cstdio>
#include<algorithm>
#include<functional>
using namespace std;
int main(void)
{
	int c,f;
	scanf("%d",&f);
	c=(f-30)/2;
	printf("%d\n",c);
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<cmath>
#include<vector>
#include<set>
#include<string>
#include<map>
#include<cassert>
using namespace std;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
typedef pair<int, int> P;
typedef pair<int, P> PP;

signed main() {
	int f; cin >> f;
	cout << (f - 30) / 2 << endl;
}

C++: #include <iostream>
using namespace std;
int main(void){
    
    
    int a,b;
    cin >>a;
    
    b = (a - 30) / 2;
    cout <<b<<endl;
    
}

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

int main() {
  int F;
  cin >> F;
  cout << (F - 30) / 2 << endl;
}

C++: #include <iostream>
using namespace std;
int main(void){
    int F;
    cin >> F;
    cout << (F-30)/2 << endl;
    return 0;
}

C++: #include <bits/stdc++.h>
#define rep0(i,n) for (int i = 0; i < (n); ++i)  //0index
#define rep1(i,n) for (int i = 1; i < (n); ++i)  //1index
#define REP(i,a,b) for (int i = a; i < (b); ++i)  //aからb - 1まで
#define mREP(i,a,b) for (int i = a; i > (b); --i)  //逆
#define all(x) (x).begin(),(x).end()
const int INF = 1000000007;  //最大値兼MOD
typedef long long ll;
using namespace std;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
int main(){
  int n;
  cin >> n;
  cout << (n - 30) / 2 << endl;
  return 0;
}

C++: #include "bits/stdc++.h"

#pragma warning(disable:4996)
using namespace std;
using ld = long double;



int main() {
	int F;cin>>F;
	cout<<(F-30)/2<<endl;
	return 0;
}

C++: #include <iostream>
using namespace std;
int main(){
    int F;
    cin>>F;
    cout<<(F-30)/2<<endl;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(a) a.begin(), a.end()
#define mod 1000000007
#define MOD 998244353
#define INF 40000000000000000
int dx8[8] = {-1, 0, 1, 1, 1, 0, -1, -1};
int dy8[8] = {1, 1, 1, 0, -1, -1, -1, 0};
int dx4[4] = {-1, 0, 1, 0};
int dy4[4] = {0, -1, 0, 1};
template <class T>
inline bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T &a, T b) {
    if(a > b) {
        a = b;
        return 1;
    }
    return 0;
}
signed main() {
    int F;cin>>F;
    cout<<(F-30)/2<<endl;
}

C++: #include <stdio.h>
#include <iostream>
#include <string>

using namespace std;

int main(){
	int F;
	cin >> F;
	cout << (F - 30) / 2
}

C++: #include <iostream>
using namespace std;
int main(void){
    // Your code here!
    int c;
    cin>>c;
    cout<<(c-30)/2<<endl;
}

C++: #include <bits/stdc++.h>
using ll = long long;
using namespace std;
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for(int i = int(a); i < int(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
const long long INFLL = 1LL << 60;
const int INFINT = 1 << 30;
const long long MOD = 1e9 + 7;

template <class T> void vecout(T V) {
    auto t = V.begin();
    while(t != V.end()) {
        cout << *t++;
        if(t != V.end()) cout << " ";
    }
    cout << endl;
};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    cout << n / 2 - 15 << endl;
}

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

#define rep(i, n) for(int i = 0; i < n; ++i)

int main() {
	int f; cin >> f; cout << (f - 30) / 2 << endl;
}

C++: #include <iostream>
using namespace std;
int main(void){
    int F,a;
    cin>>F;
    a=(F-30)/2;
    cout<<a<<endl;
}

C++: #include <iostream>
using namespace std;
int main(void){
    int a;
    cin>>a;
    cout<<(a-30)/2<<endl;
}

C++: #include<iostream>
using namespace std;

int main(){
  int F;
  cin >> F;
  cout << (F - 30) / 2 << endl;
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int main(){
    int f;
    cin>>f;
    cout<<(f-30)/2<<endl;
}

C++: #include<iostream>

using namespace std;

int F,C;


int main(){

cin>>F;

C = ( F - 30 ) / 2;

cout << C << endl;


return 0;

}

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


int main(){
	int F;
	cin >> F;	
	cout << (F-30)/2 << endl;
	return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
using namespace std;
int main(void) {
  int N;
  cin >> N;
  cout << (N-30)/2 << endl;
  return 0;
}

C++: #include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <regex>
#define ull unsigned long long
#define REP(i,n) for(int i = 0; i < n; i++)
#define FOR(i,j,n) for(int i = j; i < n; i++)
#define RFOR(i,j,n) for(int i = j-1; i >= n; i--)
#define PREC(n) fixed << setprecision(n)
#define print_array(v) REP(__k, v.size()) { cout << v[__k]; if(__k != v.size()-1) cout << " "; else cout << endl; }
using namespace std;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int F;
	cin >> F;
	cout << (F - 30) / 2 << endl;
}

C++: #include <stdio.h>
int main(void) {
	int F;
	scanf("%d", &F);
	F = (F - 30) / 2;
	printf("%d\n", F);
	return 0;
}

C++: #include <iostream>
using namespace std;
int main(void){
       int a;
       cin>>a;
       cout<<(a-30)/2<<endl;
       return 0;
    
}

C++: #include<bits/stdc++.h>

using namespace std;

main(){
	int F;
	int C;
	cin >> F;
	C=(F-30)/2;
	printf("%d\n",C);
}

C++: #include <iostream>
using namespace std;
int main(){

int C , F ;
cin >> F ;

C = ( F - 30 ) / 2;

cout << C << endl ;

return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int main(){
   int s;
   cin >> s;
   cout << (s-30)/2 << endl;
   return 0;
}

C++: #include <iostream>
using namespace std;

int main()
{
	int f;
	cin >>f;
	cout << (f - 30) / 2 << endl;
	
	
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;

int main() {
    int F;
    cin >> F;
    cout << (F-30)/2 << endl;
    return 0;
}