/in/foo.c: In function 'main':
/in/foo.c:5:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    5 |     scanf("%d",&n);
      |     ^~~~~
/in/foo.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | int main()
/in/foo.c:5:5: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    5 |     scanf("%d",&n);
      |     ^~~~~
/in/foo.c:5:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:12:20: warning: implicit declaration of function 'pow' [-Wimplicit-function-declaration]
   12 |         num=str[i]*pow(10,n-i-1);
      |                    ^~~
/in/foo.c:1:1: note: include '<math.h>' or provide a declaration of 'pow'
  +++ |+#include <math.h>
    1 | int main()
/in/foo.c:12:20: warning: incompatible implicit declaration of built-in function 'pow' [-Wbuiltin-declaration-mismatch]
   12 |         num=str[i]*pow(10,n-i-1);
      |                    ^~~
/in/foo.c:12:20: note: include '<math.h>' or provide a declaration of 'pow'
/in/foo.c:16:5: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   16 |     printf("%d",sum);
      |     ^~~~~~
/in/foo.c:16:5: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:16:5: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
/in/foo.c:16:5: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:4:13: warning: unused variable 'length' [-Wunused-variable]
    4 |     int n,i,length,num,sum=0;
      |             ^~~~~~