Cod sursă (job #819718)

#include <bits/stdc++.h>

using namespace std;
ifstream fin("scv.in");
ofstream fout("scv.out");
#define int long long
int x,c,m,t;
long long sum,nr=1;
int zi;
signed main()
{
    fin>>c>>t>>m>>x;
    while (sum<x)
    {
        if (sum>=c)
        {
            int val=x-sum;
            int val1=nr*m;
            int day1=val/val1;
            if (val%val1!=0) day1++;
            val=(x-(sum-c)-nr*m*t);
            val1=((nr+1)*m);
            int day2=val/val1+t-1;
            if (val%val1!=0) day2++;
            if (day2<day1)
            {
                sum-=c;
                sum=sum+nr*m*t;
                nr++;
                zi+=t;
            }
            else
            {
                sum=sum+nr*m;
                zi++;
            }
        }
        else
        {
            sum=sum+nr*m;
            zi++;
        }
        //cout<<sum<<" "<<zi<<'\n';
    }
    fout<<zi;
    return 0;
}