#include <stdio.h>
#include <math.h>

int
main()
{
     int n = 0, sum = 0, sumsq = 0, c;
     while ((c = getchar()) != EOF) {
          n++;
          sum += c;
          sumsq += c*c;
     }
     printf("Sample SD on %d bytes averaging %.3f is %.3f\n", 
            n,
            sum/(double)n,
            sqrt(sumsq - (double)sum*sum/n)/(n-1));
     return 0;
}