long m,a[99]={1,1};i,s;main(n){for(scanf("%d%ld",&n,&m);++i<n-1;a[i+1]=a[i]+a[i-1]);for(m=a[i--]-m;i--;m>=a[i]?m-=a[i],s++:0);s=!printf("%d",m?-1:s);}