foo.c: In function 'main':
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d,%d",&a,&b); 
  ^~~~~~~~~~~~~~~~~~~~
/tmp/cc9QWkCP.o: In function `main':
foo.c:(.text.startup+0x30): undefined reference to `lcm'
collect2: error: ld returned 1 exit status

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