Sorry to bother with a noob question. I am trying to understand how bignum.c works. For that, I'm trying to write a program to add two numbers. Here is what I have https://pastebin.com/mbRaE5i5, I'm not sure if this is the correct approach. I use the following to compile the code, 

But get the following error,

/tmp/ccMo7DMW.o: In function `main':
mpi_example.c:(.text+0x2d): undefined reference to `mbedtls_mpi_init'
mpi_example.c:(.text+0x39): undefined reference to `mbedtls_mpi_init'
mpi_example.c:(.text+0x45): undefined reference to `mbedtls_mpi_init'
mpi_example.c:(.text+0x6c): undefined reference to `mbedtls_mpi_add_int'
mpi_example.c:(.text+0x9a): undefined reference to `mbedtls_mpi_free'
mpi_example.c:(.text+0xa6): undefined reference to `mbedtls_mpi_free'
mpi_example.c:(.text+0xb2): undefined reference to `mbedtls_mpi_free'
collect2: error: ld returned 1 exit status

Any help what I'm doing wrong here? Or any sample code and how to compile it?

Thanks,

~ Shariful