ATM.cpp

#include <stdio.h>
int main(){
	int x;
	float y;
	scanf("%d %f",&x,&y);
	if(x%5==0&&0.5<=y-x){
		printf("%.2f",y-x-0.5);
	}
	else{
		printf("%.2f",y);
	}
	return 0;
}

atm.java

import java.util.Scanner;
class main{
	public static void main(String[] arg){
		Scanner in = new Scanner(System.in);
		int x;
		float y;

		x = in.nextInt();
		y = in.nextFloat();
		if (x%5==0 && x+0.5<=y){
			System.out.format("%.2f\n",y-(x+0.5));
		}
		else{
			System.out.format("%.2f\n",y);
		}
	}		
}

atm.py

x,y = raw_input().split()
x=int(x)
y=float(y)
if x%5==0 and y-0.5>=float(x) and x!=0:
	print format(y-x-0.50,".2f")
else:
	print format(y,".2f")

atm.rb

a = gets.chomp.split
x = a[0].to_f
y = a[1].to_f
if x % 5 == 0 and y > (x+0.50)
	y = y-x-0.50
end
puts "%.2f" %y