graph LR;
a1((S))-->b1((P));
a2((A))-->b1;
a3((M))-->b1;
a1-->b2((K));
a2-->b2;
a3-->b2;
a1-->b3((X));
a2-->b3;
a3-->b3;
a1-->b4((R));
a2-->b4;
a3-->b4;
b1-->c1((K));
b2-->c1;
b3-->c1;
b4-->c1;
b1-->c2((A));
b2-->c2;
b3-->c2;
b4-->c2;
c1-->d4((...));