#include <iostream>
using namespace std;
int main(){
	double a;
	scanf("%lf",&a);
	printf("%.5f",5*(a-32)/9);
	return 0;
}

/*********************************
备注:
*********************************/
#include <iostream>
#include <cstdio>
#include <iomanip>
#include <cmath>
#include <math.h>
#include <algorithm>
#include <cstring>
#include <string>
#include <stack>
#include <queue>
#include <algorithm>
#define LL long long
using namespace std;
const int INF = 0x3f3f3f3f;
const int N = 1e5 + 10;
double c , f;
int main()
{
	cin >> f;
    c = 5 * ( f - 32 ) / 9;
    cout << fixed << setprecision(5) << c;
	return 0;
}

#include<bits/stdc++.h>
#include<cstring>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#include<map>
#define ll long long
using namespace std;
const int N=1e5+10;
const int M=2023;
const int inf=0x3f3f3f3f;
double  F,C;//F代表华氏温度 C代表摄氏温度 
int main()
{
	cin>>F;
	C=5*(F-32)/9;
	printf("%.5lf",C);
	return 0;
}

#include <iostream>
#include <stdio.h>
#include <iomanip>
using namespace std;
const int N = 1e6 + 10;
const int INF = 0x3f3f3f3f;
int main()
{
	float F;
	cin >> F;
	F = 5 * ( F - 32 ) / 9;
	cout << fixed << setprecision(5) << F;
	return 0;
}

#include <iostream> 
using namespace std; 
int main() 
{
     
    double c , f ; 
    cin >> f ; 
    c = 5 * (f - 32) / 9; 
    printf("%.5lf",c);
}

return 0;

#include <iostream>
#include <bits/stdc++.h>
using namespace std;
const int N=1e7+10;
const int INF=0x3f3f3f3f;
int main()
{
	double a,b;
	cin>>a;
	b=5*(a-32)/9;
	cout<<fixed<<setprecision(5)<<b;
}

#include <bits/stdc++.h>

using namespace std;

int main(void)
{
    float f, c;

    cin >> f;

    c = 5 * (f - 32) / 9;

    cout << fixed << setprecision(5) << c;

    return 0;
}

#include<bits/stdc++.h>
using namespace std;
double C=0, F;
int main()
{
    cin >> F;
    C=5*(F-32)/9;
    printf("%.5lf", C);
}