#include<cstdio>

#include<iostream>

#include<cstring>

#include<algorithm>

#define ll long long

#define R register ll

using namespace std;

inline ll g() {

    R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;

    do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;

}

struct node {int x,y;

    bool operator <(const node& b) const{return x==b.x?y<b.y:x<b.x;}

} a[];

ll f[],p[],ans[],M[],T[];

ll fac[],inv[];

inline ll C(ll n,ll m,ll p) {

    if(n<m) return ; return fac[n]*inv[fac[m]*fac[n-m]%p]%p;

}

inline ll L(ll n,ll m,ll p) {

    if(n<m) return ; if(!n) return ;

    return L(n/p,m/p,p)*C(n%p,m%p,p)%p;

}

ll n,m,t,mod,tot,S=;

signed main() {

    n=g(),m=g(),t=g(),mod=g();

    if(mod==) p[++tot]=mod;

    else p[]=,p[]=,p[]=,p[]=,tot=;

    for(R i=;i<=t;++i) a[i].x=g(),a[i].y=g();

    sort(a+,a+t+); for(R i=;i<=tot;++i) S*=p[i];

    for(R i=;i<=tot;++i) M[i]=S/p[i]; inv[]=,fac[]=;

    for(R k=;k<=tot;++k) {

        R P=p[k]; for(R i=;i<P;++i) inv[i]=(P-P/i*inv[P%i]%P)%P;

        T[k]=inv[M[k]%P]; for(R i=;i<P;++i) fac[i]=fac[i-]*i%P;

        ans[k]=L(n+m,n,P); for(R i=;i<=t;++i) {

            f[i]=L(a[i].x+a[i].y,a[i].x,P);

            for(R j=;j<i;++j) if(a[j].x<=a[i].x&&a[j].y<=a[i].y)

                f[i]+=(P-f[j]*L(a[i].x+a[i].y-a[j].x-a[j].y,a[i].x-a[j].x,P)%P)%P;

            f[i]%=P; ans[k]+=P-L(n+m-a[i].x-a[i].y,n-a[i].x,P)*f[i]%P;

        } ans[k]%=P;

    } ll anss=; for(R i=;i<=tot;++i) anss+=ans[i]*M[i]%mod*T[i]%mod;

    printf("%lld\n",anss%mod);

}