#include <stdio.h>
#include <string.h>
int n,m,nxt[100010],l[100010],r[100010];
int route[100010],tot = 0;
int f[35][35],g[35][35],ans[35];
int min(int a,int b)
{
	//return a<b?a:b;
}
void work(int sn)
{
	int i,j,now;
	memset(f,0,sizeof(f));
	for(now=sn;now;now=nxt[now]) for(i=1;i<=32;i++) for(j=i;j<=32;j++)
	{
		/*if(i<l[now]) f[i][j] += l[now]-i;
		if(j>r[now]) f[i][j] += j-r[now];*/
	}
	//for(i=1;i<=32;i++) for(j=i;j<=32;j++) g[i][j] = min(g[i][j],f[i][j]);
}
int main()
{
	int i,j,sn,fn,ll,rr;
	memset(g,60,sizeof(g)); memset(ans,60,sizeof(ans)); ans[0] = 0;
	scanf("%d%d",&n,&m);
	for(i=1;i<=m;i++)
	{
		scanf("%d%d%d%d",&sn,&fn,&ll,&rr);
		/*if(sn == 1) route[++tot] = fn;
		else nxt[sn] = fn;*/
		//l[fn] = ll; r[fn] = rr;
	}
	for(i=1;i<=tot;i++) work(route[i]);
	//for(i=1;i<=32;i++) for(j=0;j<i;j++) ans[i] = min(ans[i],ans[j]+g[j+1][i]);
	printf("%d",ans[32]);
	return 0;
}