// includes {{{
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<deque>
#include<map>
#include<set>
#include<tuple>
#include<cmath>
#include<random>
#include<cassert>
// }}}
// #include<bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
  std::ios::sync_with_stdio(false), std::cin.tie(0);
  int n,m,p,q;
  cin >> n >> m >> p >> q;
  int ans = 0;int k = 1;
  while(n>0) {
    ans++;
    n -= m;
    if(p <= k && k <= p + q - 1) n -= m;
    k++;
    if(k == 13) k = 1;
  }
  cout << ans << endl;
  return 0;
}