#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  int N, M, P, Q;
  cin >> N >> M >> P >> Q;

  int month = 1;
  int ret = 1;
  while(true){
    if(P <= month && month < P + Q) N -= 2 * M;
    else N -= M;
    //cout << month << " " << N << endl;
    if(N <= 0) break;
    ret++;
    month++;
    if(month >= 13) month = 1;
  }

  cout << ret << endl;
  
  return 0;
}