am⁡(y)=∑n=1K+1Pm⁢n⁡(y)⁢Gn⁡(y)(tn⁡(x⁢(y)))m+1⁢∏l=1l≠nK+1(tn⁡(x⁢(y))-tl⁡(x⁢(y))),