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)
}

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

print(int(C))

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

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

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

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

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

Python: x=int(input())
print(int((x-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;
}