54. Arifmetik progressiyaning dastlabki n ta hadi yig'indisi

Agar $N$ natural son bo'lib, $1,2,3,\dots$ arifmetik progressiyaning dastlabki $4N$ ta va $1,3,5,\dots$ arifmetik progressiyaning dastlabki $3N$ ta hadlari yig'indisi teng bo'lsa, $N$ ni toping.