#include <stdio.h>
#include <algorithm>
using namespace std;

typedef struct{
    int start;
    int end;
}t_route;

int compare(t_route a, t_route b){
    return a.start < b.start;
}

t_route A[4000];
int N,M;

int main(){

    int i,j,x,y,num_t;
    scanf("%d%d",&N,&M);

    for(i = 0;i < M;i ++){
        scanf("%d%d",&A[i].start,&A[i].end);
    }

    sort(A,A+M,compare);

    int dp[M+5] = {0};
    dp[0] = 1;
    int ans = 1;

    for(i = 1;i < M; i++){
        for(j = 0; j < i; j++){
            if(A[i].start > A[j].start && A[i].start <= A[j].end){
                dp[i] = max(dp[i],dp[j]+1);
                ans = max(ans,dp[i]);
            }
        }
    }

    printf("%d",ans);

    return 0;
}