/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
 
		int a=55;
		int b=14;
		int c=990;
		System.out.println(calculate(a,b,c));
	}
 
	public static int calculate(int a,int b,int c){
		if(b>=a ||  c< b){
			return -1;
		}
		if(c%a==b){
			return c;
		}
		else{
			int r = (c-b)%a;
			return c-r;
		}
	}
}

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