#include <stdio.h>
#include <math.h>
int main(void)
{
    double n;
    printf("Please input a number within 1000:\n");
    while (1)
    {
        scanf("%lf",&n);
        if (n>0 && n<1000)
        {
            printf("The sqrt of n is %d.",(int)sqrt(n));
            break;
        }
        else
        {
            printf("Syntax error, please re-enter it.\n");
        }
    }
    return 0;
}