#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using piii = pair<pii,int>;
#define mp(a,b) make_pair(a,b)
#define fi first
#define se second
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define per(i,a,b) for(int i=a;i>=b;i--)
const ll N = 1e3+3;

ll upx(ll n, ll x){
    return (n+x-1)/x;
}
void solve(){
    ll n,a,b;cin>>n>>a>>b;
    ll x=n*a/b; if(x*b>=n*a)x--;
    if(x==0) {cout<<-1<<endl;return;}
    int q=0;while(upx(n,1<<q)>x)q++;
    cout<<q<<endl;
}

void init(){
    
}
int main(){
    ios::sync_with_stdio(false), cin.tie(0);
    init();
    //int t;cin>>t;while(t--)
    solve();
    return 0;
}