$a[40...95,40...95]$
$loc[66][50]:RMO$
Make changes to approach in a different way.
$a[0...55,0...55]$
$loc[26][10]:RMO$
$0^{th}\ row=1$
$1^{st}\ row=2$
$2^{nd}\ row=3$
.
.
.
$25^{th}\ row=26$
$Sum=1+2+3....+26=351$
Now you are standing on $26^{th}$ row and it's first element will start from $0^{th}$ column but you need to go to $10^{th}$ column, hence add $10(0,1,2....9)$
$351+10=361$
$361+1000=1361$