Cod sursă (job #819583)

#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)
    {
        sum=sum+nr*m;
        zi++;
        if (sum>=c)
        {
            int day1=(x-sum)/(nr*m);
            int day2=(x-(sum-c)-nr*m*t)/((nr+1)*m)+t;
            if (day2<day1 && day1>0 && day2>0)
            {
                sum-=c;
                sum=sum+nr*m*t;
                nr++;
                zi+=t;
            }
        }
        //cout<<sum<<" "<<zi<<'\n';
    }
    fout<<zi-1;
    return 0;
}