Go: package main

import "fmt"

func main() {
	var F int
	fmt.Scan(&F)
	fmt.Println((F - 30)/2)
}

Python: print(int((int(input()) - 30) / 2))

Python: F=int(input())
if F%2==0:
    c=(F-30)//2
    print(int(c))

Python: # coding: utf-8
# Your code here!
f=int(input())
print((f-30)//2)

Python: F = int(input())
print( (F - 30) // 2)

Python: F = int(input())
C = (F - 30) // 2
print(C)

Python: F=int(input())
C=int((F-30)/2)
print(C)

Python: F = int(input())
print(int((F-30)/2))

Python: print((int(input())-30)//2)

Python: import math
F = int(input())
print(int((F-30)/2))

Python: x = int(input())
print(int((x-30)/2))

Python: f = int(input())
print(int((f-30) / 2))

Python: print( (int(input())-30)// 2)

Python: F=int(input())
print(int((F-30)/2))

Python: F = int(input())
print(round((F - 30) / 2))

Python: F=int(input())
C=(F-30)//2
print(C)

Python: print((int(input())-30)//2)

Python: # coding: utf-8
# Your code here!

F = int(input())
print(int((F - 30) / 2))

Python: f=int(input())
C=(f-30)//2
print(C)

Python: f=int(input())
c=(f-30)//2
print(c)

Python: print((int(input())-30)//2)

Python: a=int(input())
print(int((a-30)/2))

Python: f=int(input())
print(int((f-30)/2))

Python: print((int(input())-30)//2)

Python: F=int(input())
C=(F-30)//2
print(C)

Python: F=int(input())
C=int((F-30)/2)
print(C)

Python: F=int(input())
x=F-30
C=int(x/2)
print(C)

Python: F = int(input())
print((F-30)//2)

Python: a=int(input())
c=a-30
d=int(c/2)
print(d)

Python: F = int(input())
print((F-30)//2)

Python: F=int(input())
print(int((F-30)/2))

Python: F=int(input())
C=int((F-30)/2)
print(C)

Python: print((int(input())-30)//2)

Python: x = int(input())
print(int((x-30) / 2))

Python: print((int(input())-30)//2)

Python: F=int(input())
print(int((F-30)/2))

Python: F=int(input())
C=int((F-30)/2)
print(C)

Python: print(int((int(input())-30) / 2))

Python: F=int(input())
C=int((F-30)/2)
format(C,'.0f')
print(C)

Python: f=int(input())
c=(f-30)/2
c=int(c)
print(c)

Python: 
F=int(input())
print(int((F-30)/2))

Python: F=int(input())
if F%2==0:
    print(int((F-30)/2))
else:
    pass

Python: F=int(input())
if 30<=F<=100:
    C=int((F-30)/2)
    print(C)
else:
    pass

Python: F = int(input())

C = ((F - 30) // 2)

print(C)

Python: #!/usr/bin/python3
# coding: utf-8
F = int(input())
C = int (F-30)//2

print(C)

Python: f=int(input())
c=int((f-30)/2)
print(c)

Python: # coding: utf-8
# Your code here!
x=int(input())
print((x-30)//2)

Python: F=int(input())
print((F-30)//2)

Python: a=int(input())
print((a-30)//2)

Python: F = int(input())
C = int((F-30)/2)
print(C)

Python: print( (int(input())-30)//2 )

Python: f=int(input())
c=int((f-30)/2)

print(c)

Python: F=int(input())
C=int((F-30)/2)
print(C)

Python: a=int(input())
print((a-30)//2)

Python: F =int(input())
C =int((F-30)/2)
print(C)

Python: F=int(input())
C=(F-30)/2
print(int(C))

Python: print(int(input())-30>>1)

Python: print((int(input())-30)//2)

Python: a=int(input())
print((a-30)//2)

Python: f=int(input())
print((f-30)//2)

Python: F=int(input())
C=(F-30)//2
print(C)

Python: a=int(input())
print((a-30)/2)

Python: F=int(input())
C=(F-30)//2
print(C)

Python: F=int(input())
print(round((F-30)/2))

Python: w=int(input())
print(int((w-30)/2))

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(){
    long int C,F;
    cin >>C;

    F=(C-30)/2;
    cout<< F <<endl;

    return 0;
}

C++: #line 2 "lib/template.cpp"

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using VI = vector<int>;
using VVI = vector<vector<int>>;
using VLL = vector<ll>;
using VVLL = vector<vector<ll>>;
using VB = vector<bool>;
using PII = pair<int, int>;
using PLL = pair<ll, ll>;
constexpr int INF = 1000000007;
constexpr ll INF_LL = 1'000'000'000'000'000'007;
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define newl '\n'

// loops rep(until) / rep(var, until) / rep(var, from, until) / repr (reversed order)
#define OVERLOAD3(_1, _2, _3, name, ...) name
#define rep(...) OVERLOAD3(__VA_ARGS__, REPEAT_FROM_UNTIL, REPEAT_UNTIL, REPEAT)(__VA_ARGS__)
#define REPEAT(times) REPEAT_CNT(_repeat, __COUNTER__, times)
#define REPEAT_CNT(_repeat, cnt, times) REPEAT_CNT_CAT(_repeat, cnt, times)
#define REPEAT_CNT_CAT(_repeat, cnt, times) REPEAT_FROM_UNTIL(_repeat ## cnt, 0, times)
#define REPEAT_UNTIL(name, times) REPEAT_FROM_UNTIL(name, 0, times)
#define REPEAT_FROM_UNTIL(name, from, until) for (int name = from, name ## __until = (until); name < name ## __until; name++)
#define repr(...) OVERLOAD3(__VA_ARGS__, REPR_FROM_UNTIL, REPR_UNTIL, REPEAT)(__VA_ARGS__)
#define REPR_UNTIL(name, times) REPR_FROM_UNTIL(name, 0, times)
#define REPR_FROM_UNTIL(name, from, until) for (int name = (until)-1, name ## __from = (from); name >= name ## __from; name--)

template <typename T, typename U>
bool chmin(T& var, U x) { if (var > x) { var = x; return true; } else return false; }
template <typename T, typename U>
bool chmax(T& var, U x) { if (var < x) { var = x; return true; } else return false; }
ll power(ll e, ll t, ll mod = INF_LL) {
  ll res = 1; for (; t; t >>= 1, (e *= e) %= mod) if (t & 1) (res *= e) %= mod; return res;
}
ll choose(ll n, int r) {
  chmin(r, n-r); if (r < 0) return 0; ll res = 1; rep(i, r) res *= n-i, res /= i+1; return res;
}
template <typename T, typename U> T divceil(T m, U d) { return (m + d - 1) / d; }
template <typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

// debugging stuff
#define repi(it, ds) for (auto it = ds.begin(); it != ds.end(); it++)
class DebugPrint { public: template <typename T> DebugPrint& operator <<(const T& v) {
#ifdef LOCAL
    cerr << v;
#endif
return *this; } } debugos; template <typename T> DebugPrint& operator<<(DebugPrint& os, const
vector<T>& vec) { os << "{"; for (int i = 0; i < vec.size(); i++) os << vec[i] << (i + 1 ==
vec.size() ? "" : ", "); os << "}"; return os; } template <typename T, typename U> DebugPrint&
operator<<(DebugPrint& os, const map<T, U>& map_var) { os << "{"; repi(itr, map_var) { os << *
itr; itr++; if (itr != map_var.end()) os << ", "; itr--; } os << "}"; return os; } template <
typename T> DebugPrint& operator<<(DebugPrint& os, const set<T>& set_var) { os << "{"; repi(
itr, set_var) { os << *itr; itr++; if (itr != set_var.end()) os << ", "; itr--; } os << "}";
return os; } template <typename T, typename U> DebugPrint& operator<<(DebugPrint& os, const
pair<T, U>& p) { os << "(" << p.first << ", " << p.second << ")"; return os; } void dump_func(
) { debugos << newl; } template <class Head, class... Tail> void dump_func(Head &&head, Tail
&&... tail) { debugos << head; if (sizeof...(Tail) > 0) { debugos << ", "; } dump_func(forward
<Tail>(tail)...); }
#ifdef LOCAL
#define dump(...) debugos << "  " << string(#__VA_ARGS__) << ": " << "[" << to_string(__LINE__) \
<< ":" << __FUNCTION__ << "]" << newl << "    ", dump_func(__VA_ARGS__)
#else
#define dump(...) ((void)0)
#endif


#line 2 "main.cpp"


int main() {
  cin.tie(nullptr); ios_base::sync_with_stdio(false);

  int f; cin >> f;
  cout << (f-30)/2 << newl;
}

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

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;

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