void main(){
  import std.stdio, std.string, std.conv, std.algorithm;

  long k, a, b; rd(k, a, b);

  if(a>=k){writeln(1); return;}
  auto d=a-b;
  if(d<=0){writeln(-1); return;}
  auto tmp=(k-a+d-1)/d;
  writeln(tmp*2+1);
}

void rd(T...)(ref T x){
  import std.stdio, std.string, std.conv;
  auto l=readln.split;
  assert(l.length==x.length);
  foreach(i, ref e; x){
    e=l[i].to!(typeof(e));
  }
}
void wr(T...)(T x){
  import std.stdio;
  foreach(e; x) write(e, " ");
  writeln();
}