// luogu-judger-enable-o2
#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long k,a,b,c=0;
    cin>>k>>a>>b;
    if(a>=k)
    {
        cout<<1<<endl;
        return 0;
    }
    else if(b>=a)
    {
        cout<<-1<<endl;
        return 0;
    }
    else if((k-a)%(a-b)>=1)
        c=1;
    cout<<((k-a)/(a-b)+c)*2+1<<endl;
}