#include <bits/stdc++.h>
using namespace std;

int x[ 110 ];
int y[ 110 ];

int main()
{
int i;
int N;
int M;
int P;
int Q;
int Y;
int Year;
int Mn;
int Chk;

	ios::sync_with_stdio( false );
	cin.tie( 0 );

	cin >> N;
	cin >> M;
	cin >> P;
	cin >> Q;

	Y = M * ( 12 + Q );
	Year = N / Y;
	Chk = N % Y;

	for( i = 1; i <= 11; i++ )
	{
		Chk -= M;
		if( i >= P && i < P + Q ) Chk -= M;

		if( Chk <= 0 )
		{
			cout << Year * 12 + i << endl;

			return 0;
		}
	}

	cout << Year * 12 + 12 << endl;

	return 0;
}