#include <stdio.h>
#include <stdlib.h>

unsigned forever=0;
unsigned bitmask[40];

unsigned kolik(unsigned a, unsigned b, unsigned c, unsigned k) {
  unsigned bma;
  unsigned posun,krat;
  
  bma=b-a;
  bma = bma & bitmask[k];
  if(!bma) return 0;
  
  if(c==0) {
    forever=1;
    return 0;
  }
  if(bma%c == 0) {
    return bma/c;
  }
  posun=(1<<k)%c;
  krat=(1<<k)/c;
  posun = posun & bitmask[k];
  return krat*kolik(a,b,posun,k);
}

int main(void) {
    unsigned a,b,c,k;
    unsigned i;
    unsigned r;
    
    bitmask[0]=0;
/*    printf("bitmask %8x\n",bitmask[0]);*/
    bitmask[32]=0xffffffffU;
    for(i=1;i<32;i++) {
      bitmask[i]=0xffffffffU>>(32-i);
/*      printf("bitmask %8x\n",bitmask[i]);*/
    }
     
/*    printf("bitmask %8x\n",bitmask[32]);*/

    while(1) {
      scanf("%d %d %d %d",&a,&b,&c,&k);
      if((a|b|c|k)==0) break;
      forever=0;
      r=kolik(a,b,c,k);
      if(!forever) printf("%u\n",r);
        else printf("FOREVER\n");
    }

    return 0;
}