Cod sursă (job #470709)

#include <bits/stdc++.h>

#define cin fin
#define cout fout

using namespace std;

ifstream fin("scv.in");
ofstream fout("scv.out");

int main() {
	long long mmc, tot, mase, ics;
	cin >> mmc >> tot >> mase >> ics;

	long long min = (ics - 1) / mase + 1, R = ics / mmc + 1, day = 1, m = mase;

	int i;
	for (i = 1; i <= R; i++) {
		if (m >= mmc) {
			day += tot;
			m += mase * i * tot - mmc;
		} else {
			day += (mmc - m - 1) / (mase * i) + tot + 1;
			m = m + ((mmc - m - 1) / (mase * i) + 1) * (mase * i) - mmc +
					mase * i * tot;
		}

		long long z;
		if (m >= ics) {
			z = day;
			i = R;
		} else {
			z = day + (ics - m - 1) / (mase * (i + 1)) + 1;
		}
		if (z < min) {
			min = z;
		}
	}

	cout << min;
	return 0;
}