#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>
int main(void)
{
    long long int a,b,c,d,val;
    scanf("%lld %lld %lld %lld",&a,&b,&c,&d);
    val = a*b%d;
    val*=c%d;
    printf("%lld",val);
}