import std.stdio, std.string, std.conv, std.algorithm, std.numeric;
import std.range, std.array, std.math, std.typecons, std.container, core.bitop;


void main() {
    long k,a,b;
    scan(k, a, b);

    if (a >= k) {
        writeln(1);
        return;
    }

    if (a <= b) {
        writeln(-1);
    }
    else {
        long s = a - b;
        long ans = (k - a + s - 1) / s;
        ans = 2*ans + 1;
        writeln(ans);
    }
}



void scan(T...)(ref T args) {
    string[] line = readln.split;
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}


void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}