a:20=5, rest
a=20*5+rest
a=100+rest
rest∈{0, 1, 2,...,19}
=>a∈{100, 101, 102,...,119}
=> S=100+101+102+103+104+105+106+107+108+109+110+111+112+113+114+115+116+117+118+119
S=201+102+103+104+105+106+107+108+109+110+111+112+113+114+115+116+117+118+119
S=303+103+104+...+119
S=406+104+105+...+119
S=510+105+106+...+119
S=615+106+107+...+119
S=721+107+108+...+119
S=828+108+109+...119
S=936+109+110+...119
S=1045+110+111+...119
Faci tot asa si in final iti da 2190
