#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(){
  ll a,b,c,d;
  cin >> a >> b >> c >> d;
  ll ans=0;
  if(b>=c*d){cout << -1 <<endl;return 0;}
  ll e=0;
  while(a>e*d){
    a+=b;
    e+=c;
    ans++;
  }
  cout << ans;
}
#include <bits/stdc++.h>
using namespace std;
 
int main()
{
	for( int i = 0; i < 1000; i++ ) {
		int si, sj, ti, tj;
		cin >> si >> sj >> ti >> tj;
		string ans;
		if( si < ti ) {
			ans += string( ti - si, 'D' );
		}
		else if( si > ti ) {
			ans += string( si - ti, 'U' );
		}
		if( sj < tj ) {
			ans += string( tj - sj, 'R' );
		}
		else if( sj > tj ) {
			ans += string( sj - tj, 'L' );
		}
		cout << ans << endl;
		int d;
		cin >> d;
	}
}
