process.stdin.resume();
process.stdin.setEncoding('ascii');

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

function howManyGames(p, d, m, s) {

  var val = p, res = 0;

  while (true) {
    s -= val;
    res++;

    if (s < 0)
      break;

    val -= d;

    if (val < m)
      val = m;
  }

  return res - 1;

}

function main() {
    var p_temp = readLine().split(' ');
    var p = parseInt(p_temp[0]);
    var d = parseInt(p_temp[1]);
    var m = parseInt(p_temp[2]);
    var s = parseInt(p_temp[3]);
    var answer = howManyGames(p, d, m, s);
    process.stdout.write("" + answer + "\n");

}