C++ :

#include<iostream>
using namespace std;
int main()
{
	int n,day=0;
	cin>>n;
	n*=1000;
	while (n>0)
	{
		n+=50;
		n-=3000;
		day++;
	}
	cout<<day<<endl;
	return 0;
}

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input=new Scanner(System.in);
		int n=input.nextInt();
		int count=0;
		int sum=50;
		if(n%3==0) {
			count=n/3;
			sum*=count;
		}else {
			count=n/3+1;
			sum*=count;
		}
		if(sum>3000) {
		 if(sum%3000==0) {
			 count++;
		 }else {
			 sum=sum/3000;
			 count+=sum;
		 }
		}else {
			count++;
		}
		System.out.println(count);
	}
}