/in/foo.c: In function 'main':
/in/foo.c:11:23: warning: implicit declaration of function 'pow' [-Wimplicit-function-declaration]
   11 |                 Sn=Sn+pow(a,i);
      |                       ^~~
/in/foo.c:2:1: note: include '<math.h>' or provide a declaration of 'pow'
    1 | #include <stdio.h>
  +++ |+#include <math.h>
    2 | 
/in/foo.c:11:23: warning: incompatible implicit declaration of built-in function 'pow' [-Wbuiltin-declaration-mismatch]
   11 |                 Sn=Sn+pow(a,i);
      |                       ^~~
/in/foo.c:11:23: note: include '<math.h>' or provide a declaration of 'pow'