Cod sursă (job #105655)

#include<cstdio>
using namespace std;

int main(){
    freopen ("scv.in","r",stdin);
    freopen ("scv.out","w",stdout);
    long long x,c,m,t;
    int i;
    long long min,z;
    long long rob,zi,bani;

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

    rob=x/c+1;
    zi=1;
    min=(x-1)/m+1;
    bani=m;
    for(i=1;i<=rob;i++){
        if (bani>=c){
            zi+=t;
            bani=bani+m*i*t-c;
        }
        else {
            zi=zi+(c-bani-1)/(m*i)+1+t;
            bani=bani+((c-bani-1)/(m*i)+1)*(m*i)-c+m*i*t;
        }
        if (bani>=x){
            z=zi;
            i=rob;
        }
        else z=zi+(x-bani-1)/(m*(i+1))+1;

        if (z<min) min=z;
    }

    printf ("%lld",min);
    return 0;
}