Linux and C

Write a program that will calculate the nthelement of such an extended Fibonacci sequence. For example, assuming that your executable program was called efib and that the shell prompt is "bash-4.4$ ", interaction with your program might be as follows: bash-4.4$./efib Enter a number: 0 F(0) is 0 bash-4.4$ /efib Enter a number: 1 F (1) is 1 bash-4.4$./efib Enter a number:1 P (-1) is 1 bash-4.4$ /efib Enter a number: 6 F(6) is 8 bash-4.4$/efib Enter a number-9 F(-9) is 34 bash-4.4$ ./efib Enter a number:10 F(-10) is -55 bash-4.4$