#include<bits/stdc++.h>
using namespace std;
int f(int m,int k,int s,int b)
{
	double h=m;
	int n=1;
	bool u=false;
	const double e=1e-9;
	while(true)
	{
		int t=s+n-1;
		double a=1.0*k*n;
		if(b==n&&!u)
		{
			h-=0.1*m;
			u=true;
			if(h<=e)return n;
		}
		double d=a*t;
		if(h<=d+e)return n;
		h-=d;
		n++;
	}
}
int main()
{
	int m,k,s;
	cin>>m>>k>>s;
	int r=INT_MAX;
	r=min(r,f(m,k,s,0));
	for(int x=1; x<=2000; x++)r=min(r,f(m,k,s,x));
	cout<<r<<endl;
	return 0;
}