import java.util.*;
class ValidPerfectSquare {
public boolean isPerfectSquare(int num) {
long high = (long) num+1;
long low = -1;
while(low!=high-1){
long mid = (low+high)/2;
if(mid*mid==num) return true;
else if(mid*mid>num) high = mid;
else low = mid;
}
return false;
}
}