// CBC encrypt
//
#include <stdio.h>
#include <stdlib.h>

double drand(void) { return rand()/(RAND_MAX+1.0); } // random value in the range [0.0,1.0)

int main( void)
{
  double r, plain, cipher, prev = 0;

  srand(123456); // replace 123456 with the first six digits of your number from a6/p2

  while( scanf("%lf",&plain) == 1) // until error or end-of-file
  {
    r = 20*drand() - 10; // random value -10.0 ... +10.0

    cipher = plain + prev + r; // CBC encrypt using addition

    printf("%g\n", cipher);

    prev = cipher; // save for previous ciphertext
  }

  return 0;
}