Cod sursă (job #468472)

typedef long long ll;
#include <fstream>
#include <cmath>
using namespace std;

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

ll c,T,t,m,x,s,scv=1,r1,r2,p,sm,s1,par;

int main()
{
	cin>>c>>T>>m>>x;
	
	
	for(;;)
		{
			s1=s;
			sm=scv*m;
			if(s>=c) par=0; else par=c-s;
			r1=ceil(par/(float)sm);
			r2=T*sm;
			p=s1+r1*sm-c+r2;
			if(s1>=c) s=s+p; else s=p;
			if(r1+T+ceil((x-s)/(float)((scv+1)*m)) >=ceil((x-s1)/(float)sm))
				{
					cout<<t+ceil((x-s1)/(float)sm);
					break;
				}
			else
				{
					scv++;
					t+=r1+T;
				}
		}
	

}