foo.c: In function 'main':
foo.c:18:5: warning: implicit declaration of function 'isPrime'; did you mean 'isprime'? [-Wimplicit-function-declaration]
   18 |  if(isPrime(x)==1)
      |     ^~~~~~~
      |     isprime
foo.c:17:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   17 |  scanf("%d",&x);
      |  ^~~~~~~~~~~~~~
/usr/bin/ld: /tmp/cctl1cqP.o: in function `main':
foo.c:(.text.startup+0x30): undefined reference to `isPrime'
collect2: error: ld returned 1 exit status

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