package zad1;
import java.io.*;
import java.util.*;

public class Main {

  public static void main(String[] args) {
    String fname = System.getProperty("user.home") + "/iter.txt";
    File f =  new File(fname);
    int sum = 0;
    int start = 0;
    int end = 0;
    int limit = 0;
    try {
    	Scanner scan = new Scanner(f);
    	start = scan.nextInt();
		end = scan.nextInt();
		limit = scan.nextInt();
	    for (int i = start; i <= end; i++) {
	    sum += i;
	    if (sum >= limit) break;
	    }
	    if (sum <= limit) {
	    System.out.println(sum);}
	    else {System.out.println(limit);}
    } catch (Exception exc) {
    	System.out.println("***");
    }
  }
  }