fete/(fete+baieti) =0,2=2/10=1/5
fete/(fete+16)=1/5
5fete=fete+16
4fete=16
fete=4
elevi=fete+baieti=4+16=20
7=3*2+1, numr prim
13=3*4+1, numar prim
31=3*10+1, numar prim
16=3*5+1, p.p
25=3*8+1,p.p.
100=3*33+1, p.p
3n+1+3m+1+3p+1+3r+1=3(m+n+r+p)+3+1=3(m+n+r+p+1)+1=3s+1 impartit la 3 da rerst 1, deci nu e divizibil cu 3
a=4-5=-1
atunci
1-2+3-4=2017-2018=-1-1-..-1 (1009 de -1)=-1009
