B. Potato War 1
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
"If you know the enemy and know yourself, you need not fear the result of a hundred battles." - Sun Tzu, The Art of War

Technoblade is famous for always taking things to the extreme. One day he was planting potatoes and, after seeing the size of his huge plantation, he became curious to know how long it would take for him to become the person with the most potatoes. After investigation, Techno did the math and saw that he has $$$X_1$$$ potatoes and produces $$$Y_1$$$ potatoes per day, while his biggest competitor, Squid Kid, has $$$X_2$$$ potatoes and produces $$$Y_2$$$ potatoes per day.

He will declare himself victorious of the 1st Potato War if he has a strictly greater number of potatoes than Squid. Help Techno predict the outcome of this battle.

Input

The input is just one line with 4 integers $$$X_1,Y_1,X_2,Y_2$$$ separated by space, in this order. It is guaranteed that all numbers are greater than or equal to 0 and less than or equal to 1000.

Output

If Technoblade is destined for success and victory in the 1st Potato War, print the smallest number of days until he has strictly more potatoes than SquidKid. If he still doesn't have a large enough plantation, and won't win the battle in a finite time, print $$$-1$$$.

Examples
Input
1000 0 999 1000
Output
0
Input
0 1 1000 0
Output
1001
Input
100 2 200 1
Output
101