Break-Even Point

Time limit0.35sMemory limit128 MB

Summary

Given fixed cost A, variable cost B, and price C, find the smallest number of laptops where revenue exceeds total cost, or -1 if impossible.

Level: Easy2 of 10
Topics: Math, Implementation
Solved: No attempts yet

Problem

World Electronics manufactures and sells laptops. Regardless of how many laptops it sells, it pays a fixed annual cost of A ten-thousand won. Each laptop also adds a variable production cost of B ten-thousand won.

The selling price of one laptop is C ten-thousand won. If the company sells n laptops, its total revenue is Cn and its total cost is A + Bn. In this problem, the break-even point is the smallest number of laptops for which total revenue becomes strictly greater than total cost.

Given A, B, and C, write a program that finds the break-even point.

Input

The first line contains the natural numbers A, B, and C in order, separated by spaces. Each value is at most 2,100,000,000.

Output

Print the first sales quantity that produces profit. If no break-even point exists, print -1.

Hint

The break-even point used in this problem may differ from the accounting definition.

Examples3

Example 1
Input
```
1000 70 170
```
Expected output
```
11
```
Example 2
Input
```
3 2 1
```
Expected output
```
-1
```
Example 3
Input
```
2100000000 9 10
```
Expected output
```
2100000001
```