Shell Script to find sum of n numbers

Program

#! /bin/bash
sum=0
i=1
echo "Enter the number of terms:"
read n
echo "Enter the numbers:"
while  [ $i -le $n ] 
do
  read a
  sum=`expr $a + $sum`
  i=`expr $i + 1`
done
echo "Sum is $sum"

Output

$ ./sum-of-n-numbers.sh 
Enter the number of terms:
6
Enter the numbers:
14
21
36
10
2
36
Sum is 119