Cod sursă (job #441293)

#include <fstream>
#include <climits>

using namespace std;

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

int main()
{
    long long c, m, x, s = 0, k = 1, timp = 0;
    int t;
    in >> c >> t >> m >> x;
    while (s < x)
    {
        while (s < c && s < x)
        {
            ++timp;
            s += k * m;
        }
        if (k * m * t + m * k * (c / m) + s < x)
        {
            s += t * k * m - c;
            ++k;
            timp += t;
        }
        else
        {
            while (s < x)
            {
                s += k * m;
                ++timp;
            }
        }
    }
    out << timp;
    return 0;
}