daca am sti cate bancnote sunt in total, solutia ar fi unica
asa, vom avea mai mlte solutii
fie n bancnote de 5 lei si m de 10 lei
5n+10m=800
5(n+2m)=5*160
n+2m=160
=> n par n=2k
2k+2m=2*80
k+m=80
(k,m)∈{(0,80),(1,79),(2,78),...(80,0)}, n=2k
deci (n,m)∈{(0,80),(4,78),(6,77),....(160,0)}
O zi buna!
