PROGRAMMING:Finding the sum of n terms of Fibonacci sequence

Known Fibonacci sequence has the following characteristics: the first and second numbers are 1 and 1. Start with the third number, which is the sum of the first two numbers. That is, the sequence is 1,1,2,3,5,8,13. This problem requires the preparation of procedures to calculate the number of the first N and.
###Input format:
Enter n (2 $$$Leq $$n $$$Leq $$40) from the keyboard.
###Output format:
Sum = s, s is the sum of the first n terms of Fibonacci sequence.
###Input example:
```in
ten
```
###Output example:
```out
sum=143
```







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