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