#include <stdio.h>

int main () {
  double x, y;
  int a, b;
  double pot;  			/* para calcular uma potencia */
  int j;			/* fatores jah multiplicados */
  double soma;                  /* soma parcial das potencias */
  
  scanf ( "%lf %lf %d %d", &x, &y, &a, &b );
  soma = 0;

  /* Calcula x^a */
  pot = 1;
  for ( j = 0; j < a; j++ )
    pot = pot * x;
  soma = soma + pot;

  /* Calcula y^b */
  pot = 1;
  for ( j = 0; j < b; j++ )
    pot = pot * y;
  soma = soma + pot;

  /* Calcula (x-y)^(a+b) */
  pot = 1;
  for ( j = 0; j < a+b; j++ )
    pot = pot * (x-y);
  soma = soma + pot;

  /* imprime x^a + y^b + (x-y)^{a+b} */
  printf ( "%g\n", soma );

  return 0;
}