The following problem is from codechef.com:Recently Chef become very much interested in perfect squares. We all  know Chef and his weird interests. Anyways Chef will be soon writing  his masters thesis on perfect squares revealing what-not-known  properties of perfect squares. While doing his research, he happened  to be confronted with some interesting perfect squares. These prefect  squares consists only of digits which are themselves perfect squares.  0, 1, 4 and 9 are such digits. These are called perfect digits.As we all know Chef also has habit of asking too many questions, he is  asking- given two numbers a and b, how many perfect squares exists  between these two numbers inclusive, that contains only perfect  digits.Input:First line of input will contains T, number of test cases. Then T  lines follows, each containing two positive integers a and b.Constraints:\$T \le 500\$\$1 \le a \le b \le 10000000000\$Output:For each input, output number of perfect digit squares between given  numbers. Sample:Input:21 10100 10000 Output:39How can I decrease the running time of my solution?#include<stdio.h>int main(){    int test;    long long int num1,num2,start,stop,i,j,square,rem;    scanf(%d,&test);    while(test--)    {        long long int count=0;        scanf(%lld%lld,&num1,&num2);        start=sqrt(num1);        stop=sqrt(num2);        for(i=start;i<=stop;i++)        {            square = i*i;            if(square<num1)            {                continue;            }            else            {                while(1)                {                    rem=square%10;                    if(rem!=1 && rem!= 4 && rem!=9 && rem!=0 )                    {                        break;                    }                    if(square>=10)                    {                        square=square/10;                    }                    else                    {                        if(square!=1 && square!= 4 && square!=9 &&square!=0 )                        {                                break;                        }                        else                        {                            count+=1;                        }                        break;                    }                }            }        }        printf(%lld\n,count);    }    return 0;}
Find perfect squares between two numbers
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