C :

#include<stdio.h>
void main()
{
	int n;
	double p;
	scanf("%d",&n);
	if(n>=30){ 
		p=n;
 	}else if(n>=20&&n<=29){
 		p=1.2*n;
	}else if(n>=10&&n<=19){
		p=1.5*n;
	}else{
		p=1.8*n;
	}
	printf("%.1f",p);
} 

C++ :

#include <bits/stdc++.h>
using namespace std;
int main(){
   int a;
   double b;
   cin>>a;
   if(a >= 30){
   	  b = a * 1;
   }else if(a >= 20){
   	  b = a *1.2;
   }else if(a >= 10){
   	  b = a * 1.5;
   }else{
   	  b = a * 1.8;
   } 
   cout<<fixed<<setprecision(1)<<b<<endl;
   return 0;
}

Pascal :

var a:longint;
b:real;
begin
read(a);
if a>=30 then b:=a
else if a>=20 then b:=a*1.2
else if a>=10 then b:=a*1.5
else b:=a*1.8;
write(b:0:1);
end.

Java :

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		double s = 0 ;
		if(a>=30) {
			s = (double)a;
		}else if (a>=20 ) {
			s = 1.2* (double)a ;
		}else if (a>=10) {
			s = 1.5*(double)a ;
		}else {
			s = 1.8*(double)a ;	
		}
		System.out.println(s);
	}
}

Python :

n=int(input())
if n>=30:
    s=n
elif n>=20:
    s=n*1.2
elif n>=10:
    s=n*1.5
else:
    s=n*1.8
print('%.1f'%s)