/in/foo.c: In function 'main':
/in/foo.c:35:7: warning: implicit declaration of function 'SetInster' [-Wimplicit-function-declaration]
  n3 = SetInster(a1, n1, a2, n2, a3);
       ^~~~~~~~~
/in/foo.c:24:2: warning: 'n' is used uninitialized in this function [-Wuninitialized]
  for (i = 0; i < n; i++) {
  ^~~
/tmp/ccVOQkai.o: In function `main':
foo.c:(.text.startup+0x69): undefined reference to `SetInster'
collect2: error: ld returned 1 exit status