#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,c;
	cin>>a>>b>>c;
	int t=b/c*c;
	if(t>=a)
	{
		cout<<t;	
	} 
	else
	{
		cout<<-1;
	}
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,c;
	cin>>a>>b>>c;
	int t=b/c*c;
	if(t>=a)
	{
		cout<<t;	
	} 
	else
	{
		cout<<-1;
	}
	return 0;
}