Cod sursă (job #128415)

#include <cstdio>
#include <algorithm>

using namespace std;

long long c , t , m , x , tmp , zile_nou , ramas , copie , SCV , SOL;

long long timp(long long nr , long long m , long long cost)
{
    if (cost <= 0) return 0;
    long long cat = cost / (nr * m);
    if (cost % (nr * m) == 0) return cat;
    return cat + 1;
}

int main()
{
    freopen("scv.in","r",stdin);
    freopen("scv.out","w",stdout);

    scanf("%lld %lld %lld %lld", &c , &t , &m , &x);

    /// c - costul unui nou SCV
    /// t - timpul unui nou SCV
    /// m - cantitatea pe zi
    /// x - target

    SCV = 1LL; tmp = timp(SCV , m , x); SOL = zile_nou = tmp;

    for ( ; SCV < x ; ++SCV)
    {
        zile_nou -= timp(SCV , m , x - ramas); copie += zile_nou;
        zile_nou = timp(SCV , m , c - ramas); ramas += SCV * zile_nou * m - c;
        zile_nou += t; ramas += SCV * t * m;
        zile_nou += timp(SCV + 1 , m , x - ramas);

        SOL = min(SOL , zile_nou + copie);

        if (SOL != zile_nou + copie) break;

    }

    printf("%lld\n", SOL);

    return 0;
}