#include #include #include # define EPS 10E-10 int main(void){ int X,Y,N; long double r, dx,qn; while (1){ scanf("%d %d %d %Lf", &X, &Y, &N, &r); if (X==0&&Y==0&&N==0&&r==0) break; N*=12; r/=12; r/=100; qn=pow((r+1),N); dx=X*qn-(Y/r)*(qn-1); if (dx