C :

#include<stdio.h>

void main(){
	int x;
	double p;
	scanf("%d",&x);
	
	p=0.9*x;
	
	printf("%.1f",p);
}

C++ :

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	cin>>n;
	cout<<fixed<<setprecision(1)<<(n+n*0.8+n*0.9) / 3;
}

Java :

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double x = sc.nextDouble();
		double a = x * 0.8;
		double b = x * 0.9;
		double p =(double) (x + a + b) / 3;
		System.out.println(String.format("%.1f", p));
	}
}

Python :

a=int(input())
b=a*0.8
c=a*0.9
print("%.1lf"%((a+b+c)/3))