!/bin/sh

read N

firstDiagonal=0
secondDiagonal=0
d=0
for i in $(seq $N);
do
   IFS=" "
   read -a line
   let firstDiagonal+=$((${line[$d]}))
   let secondDiagonal+=$((${line[(($N-$d-1))]}))
   let d+=1
done

result=$(($firstDiagonal-$secondDiagonal))
echo ${result#-}