/in/foo.c: In function 'main':
/in/foo.c:26:6: warning: implicit declaration of function 'LCM' [-Wimplicit-function-declaration]
    m=LCM(m,a[i]);
      ^~~
/tmp/ccGplH6C.o: In function `main':
foo.c:(.text.startup+0x9f): undefined reference to `LCM'
collect2: error: ld returned 1 exit status