PROGRAMMING:The sum of the elements of the lower left triangle of a square matrix

Enter a 4 × 4 array, find a 4 × The sum of the elements of the lower left triangle (including the main diagonal) of the array.
###Input format:
Enter a square matrix of 4 rows and 4 columns. There is no space before the first number in each row, and there is a space between each number in each row.
###Output format:
Directly output the sum of the elements of the lower left triangle (including the main diagonal). There are no additional characters
###Input example:
```in
1 2 3 4
5 6 7 8
9 1 2 3
4 5 6 7
```
###Output example:
```out
forty-six
```






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