#include <stdio.h>
long long ns[300001];
long long ms;

int main(){
    int n,m;
    scanf("%d", &n);
    scanf("%d", &m);
    for(int i = 0; i < n; i++){
        scanf("%lld", &ns[i]);
        if(i > 0 && ns[i] > ns[i - 1])
            ns[i] = ns[i - 1];
        //printf("%lld\n", ns[i]);
    }
    int high = n;
    for(int i = 0; i < m; i++){
        scanf("%lld", &ms);
        int curr_high = high - 1;
        if(curr_high >= 0){
            while(curr_high >= 0 && ns[curr_high] < ms){
                curr_high--;
            }
            high = curr_high;
        }
        else{
          high = -1;
        }
        //printf("%d\n", high);
    }
    printf("%d\n", high + 1);
    return 0;
}