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 vallet = s-p;
    var i, price = p;
    if(vallet >= 0) i=1;
    else i=0
    while(vallet > 0){
        if(price-d > m) price-=d;
        else price =m;
        vallet-=price;
        if(vallet >= 0) i++;
        //console.log(vallet+" : "+price);
    }
    return i;
}

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");

}