#import <stdio.h>

double sqrt(double x) {
    double         xHalf = 0.5 * x;
    long long int  tmp   = 0x5FE6EB50C7B537AAl - ( *(long long int*)&x >> 1);//initial guess
    double         xRes  = * (double*)&tmp;
    
    xRes *= ( 1.5 - ( xHalf * xRes * xRes ) );
    xRes *= ( 1.5 - ( xHalf * xRes * xRes ) );
    xRes *= ( 1.5 - ( xHalf * xRes * xRes ) );
    xRes *= ( 1.5 - ( xHalf * xRes * xRes ) );
    return xRes * x;
}

int main(){
    long n;
    scanf("%ld",&n);
    n=sqrt(n);
    printf("%ld", n*n);
}
