#include <stdio.h>

typedef struct {
  unsigned long long int a;
  unsigned long long int b;
  unsigned long long int c;
  unsigned long long int d;
} numsInfo;

int main(void)
{
  numsInfo data;

  scanf("%llu%llu%llu%llu", &data.a, &data.b, &data.c, &data.d);
  printf("%llu\n", ((data.a * data.b) % data.d * data.c) % data.d);

  return 0;
}