Cod sursă (job #466013)

#include <fstream>
using namespace std;

ifstream cin("scv.in");
ofstream cout("scv.out");

long long c, t, m, x, scv = 1, curKg, curT;

int main() {
	cin >> c >> t >> m >> x;
	while(curKg < x) {
		while(curKg < x && curKg < c)
			curKg += m * scv,
			curT++;
		if(curKg + scv * t * m + m * scv * (c / m) < x)
			curT += t,
			curKg += scv * t * m - c,
			scv++;
		else
			while(curKg < x)
				curT++,
				curKg += m * scv;
	}
	cout << curT;
	return 0;
}