#define MD 998244353
ll@h,@w,@n,@p,x[n],y[n];
rd((x--,y--)(n));
sortA(n,y,x);
segtree_Point_Maxval<ll> t;
t.malloc(h,1);
rep(i,n){
	ll v=t.getMaxVal(0,x[i]+1);
	t.change(x[i],v+1);
}
ll z=t.getMaxVal(0,h);
wt(1-(1-Mint(1)/p)**(h+w-3-z)*(1-Mint(2)/p)**z);