/in/foo.cc: In function 'int main()':
/in/foo.cc:65:27: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
    a[++tot].u=i+n,a[tot].v=last,a[tot].l=sqrt(1ll*(ay[i]-ax[last])*(ay[i]-ax[last])+1ll*C*C);
                   ~~~~~~~~^~~~~