Can you please tell my why do I keep getting CE when I submit this?

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    int a;
    while(cin>>a){
                  float b;
                  b=sqrt(a);
                  printf("%.4f\n",b);
                  }
    return 0;
}

When I compile it on my computer there are no errors. I'we tested and when I remove b=sqrt(a); it seems to compile. What's the problem with that?
Thanks in advice.