import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string;

auto rdsp(){return readln.splitter;}
void pick(R,T)(ref R r,ref T t){t=r.front.to!T;r.popFront;}
void readV(T...)(ref T t){auto r=rdsp;foreach(ref v;t)pick(r,v);}

void main()
{
  int n, m, p, q; readV(n, m, p, q);

  auto r = 1;
  for (;;)
    foreach (mo; 1..13) {
      n -= m;
      if (mo >= p && mo < p+q) n -= m;
      if (n <= 0) {
        writeln(r);
        return;
      }
      ++r;
    }
}