/in/foo.c: In function 'isshuixianhuashu':
/in/foo.c:8:24: warning: implicit declaration of function 'pow' [-Wimplicit-function-declaration]
    8 |         int cube_sum = pow(hundreds,3)+pow(tens,3)+pow(units,3);
      |                        ^~~
/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:8:24: warning: incompatible implicit declaration of built-in function 'pow' [-Wbuiltin-declaration-mismatch]
    8 |         int cube_sum = pow(hundreds,3)+pow(tens,3)+pow(units,3);
      |                        ^~~
/in/foo.c:8:24: note: include '<math.h>' or provide a declaration of 'pow'
/in/foo.c: In function 'main':
/in/foo.c:13:14: error: 'i' undeclared (first use in this function)
   13 |         for (i=100;i<1000;i++){
      |              ^
/in/foo.c:13:14: note: each undeclared identifier is reported only once for each function it appears in