/in/foo.c: In function 'main':
/in/foo.c:6:5: warning: implicit declaration of function 'sacnf' [-Wimplicit-function-declaration]
     sacnf("%d",&n);
     ^~~~~
/tmp/ccxNs9no.o: In function `main':
foo.c:(.text.startup+0x13): undefined reference to `sacnf'
collect2: error: ld returned 1 exit status