#include <bits/stdc++.h>
using namespace std;

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FORR(x,arr) for(auto&& x:arr)
#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,a,b) for (int i = (b)-1; i >= (a); i--)
#define REP(i,n) for (int i = 0; i < (n); i++)
#define RREP(i,n) for (int i = (n)-1; i >= 0; i--)
#define ALL(x) (x).begin(), (x).end()
#define BIT(n) (1LL<<(n))
#define SZ(x) ((int)(x).size())
#define fst first
#define snd second
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl
typedef long long ll;
// -------------------------------------

void Main() {
  ll a,b,c,d;
  cin >> a >> b >> c >> d;
  cout << (a * b % d) * c % d << endl;
}
int main() { cin.tie(0); ios::sync_with_stdio(false); Main(); return 0; }