#include<bits/stdc++.h>
int main()
{
	int meal,cook,need;
	std::cin>>meal>>cook>>need;
	double left[cook];
	for(int v=0;v<cook;v+=1)
	{
		int s;
		std::cin>>s;
		left[v]=-s;
	}
	int ti=0,have;
	while(true)
	{
		have=0;
		ti+=1;
		for(int u=0;u<cook;u+=1)
		{
			if(left[u]<0){left[u]+=1;}
			else
			{
				left[u]+=1.0/need;
				if(fabs(ceil(left[u])-left[u])<=0.000001){have+=ceil(left[u]);}
				else{have+=int(left[u]);}
			}
		}
		if(have>=meal){break;}
	}
	std::cout<<ti;
	return 0;
}