Răspuns :
Folosind formula lui Gauss 1+2+3+......+n = n(n+1):2 obtinem
n = 199
199(199+1):2 = 199*200:2 = 199*100 = 19900
n = 199
199(199+1):2 = 199*200:2 = 199*100 = 19900