How to solve Error using ==> fchcode at The input curve is broken or points are out of order in matlab

i am using a chaincode from the DIPUM toolbox and i have a character image R it is very clear and the function work correctly till the chain code is put on,i have this as a code g = bound2im(b, M, N); [s, su] = bsubsamp(b, 50); cn = connectpoly(s(:, 1), s(:, 2)); c = fchcode(su); after this code error came The input curve is broken or points are out of order.

please suggest us..