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

struct cw{
    int m1,m2;
};

int c,l,num;
cw a[11086];
cw ow[11086];

bool cmp1(cw a,cw b){
    if(a.m2==b.m2)return a.m1<b.m1;
    return a.m2<b.m2;
}

int main () {
    freopen("tanning.in","r",stdin);
    freopen("tanning.out","w",stdout);
    
    cin>>c>>l;
    for(int i = 1; i<=c; i++){
        cin>>ow[i].m1>>ow[i].m2;
    }
    for(int i = 1; i<=l; i++){
        cin>>a[i].m1>>a[i].m2;
    }
    sort(ow+1,ow+1+c,cmp1);
    
    for(int i = 1; i<=c; i++){
        int mn=ow[i].m2+1,h=-1;
        for(int j = 1; j<=l; j++){
            if(mn>=a[j].m1&&a[j].m2>0&&a[j].m1>=ow[i].m1&&a[j].m1<=ow[i].m2){
                mn=a[j].m1;
                h=j;
            }
        }
        if(h!=-1){if(num<l)num++; a[h].m2--;}
    }
    
    cout<<num;
    
    return 0;
}