/in/foo.c: In function 'main':
/in/foo.c:6:10: warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int' [-Wformat=]
  scanf("%d",x);
          ^
/in/foo.c:10:9: warning: implicit declaration of function 'sqrt' [-Wimplicit-function-declaration]
   int n=sqrt(x1);
         ^~~~
/in/foo.c:10:9: warning: incompatible implicit declaration of built-in function 'sqrt'
/in/foo.c:10:9: note: include '<math.h>' or provide a declaration of 'sqrt'
/in/foo.c:14:6: error: 'i' undeclared (first use in this function)
   if(i>n)
      ^
/in/foo.c:14:6: note: each undeclared identifier is reported only once for each function it appears in