ll C[2d5][4],t;void f(ll i){rep(j,4)if(t=C[i][j])rep[C[t-1]](s,4)if(s==i+1)s=0,wtN("("),f(t-1),wtN("methyl)");}{ll@N;rep(i,N)rep(j,4){string@c;C[i][j]=c<"H"?stoi(c):0;}f(0);wt("methane");}