foo.c: In function 'main':
foo.c:8:11: warning: implicit declaration of function 'sqrt' [-Wimplicit-function-declaration]
   if((int)sqrt(i)==sqrt(i))
           ^~~~
foo.c:8:11: warning: incompatible implicit declaration of built-in function 'sqrt'
foo.c:8:11: note: include '<math.h>' or provide a declaration of 'sqrt'

[Hydro](https://hydro.ac)提供评测服务