/in/foo.cc: In function 'int main()':
/in/foo.cc:11:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int num_1 = 1; num_1 < INITNUM; ++num_1)
                         ~~~~~~^~~~~~~~~
/in/foo.cc:10:9: warning: unused variable 'num_1' [-Wunused-variable]
     int num_1,num_2;
         ^~~~~
/tmp/ccq6UHJN.o: In function `main':
foo.cc:(.text.startup+0x32): undefined reference to `divsum(int)'
foo.cc:(.text.startup+0x3f): undefined reference to `divsum(int)'
collect2: error: ld returned 1 exit status