a,b,c,d,s;main(t){scanf("%d%d%d%d",&d,&a,&b,&c);a>c?a^=c^=a^=c:a==c?s++,a=a<d?0:a-d:0;a=!(a<b&c<b|a>b&c>b&&c?putchar(48+s):(a|c)&&d?t=(c-b)/d+1,t=a|t*d<c?t+s+(t*d+a==c):-1,c=(b-a)/d+1,printf("%d",a|c*d<b&&c<t?c+s:t):puts("-1"));}