#include<bits/stdc++.h>
#include<unordered_set>
using namespace std;
#define fio ios_base::sync_with_stdio(false)

#define ll long long int
#define s3(x,y,z) s(x)+s(y)+s(z)
#define s(x) scanf("%lld",&x)
#define p(x) printf("%lld\n",x)
ll n,m,x,y;

bool solve(ll z){
  return (z*x<=m+(n-z)*y);
}

int main()
{

  ll t=1;
  // s(t);
  while(t--){
      s3(n,m,x);
      s(y);
      ll lo=0;
      ll hi=n;
      ll ans=0;
      while(lo<=hi){
        ll mid=lo+hi;
        mid>>=1;
        if(solve(mid))
        {
          lo=mid+1; ans=mid;
        }
        else hi=mid-1;
      }
      p(ans);
  }
  return 0;
 }