#include<cstdio>

#include<iostream>

#include<queue>

using namespace std;

struct point{

    int x,y,time;

}start;

int vis[][][] = {},a[][][] = {},dir[][] = {{-,},{,},{,-},{,}};

int main()

{

    int n,m,t;

    scanf("%d%d%d",&n,&m,&t);

    while(t--)

    {

        int x,y,start,stop;

        scanf("%d%d%d%d",&x,&y,&start,&stop);

        a[x][y][] = start;

        a[x][y][] = stop;

    }

    start.x = ;

    start.y = ;

    start.time = ;

    queue<point> q;

    q.push(start);

    while(!q.empty())

    {

        int x = q.front().x,y = q.front().y,time = q.front().time;

        if(x == n && y == m)

        {

            printf("%d\n",time);

            return ;

        }

        q.pop();

        for(int i = ;i < ;i++)

        {

            int xx = x+dir[i][],yy = y+dir[i][],timee = time+;

            if(xx <  || xx > n || yy <  || yy > m || timee>=a[xx][yy][]&&timee<=a[xx][yy][] || vis[xx][yy][timee])    continue;

            point temp;

            temp.x = xx;

            temp.y = yy;

            temp.time = timee;

            q.push(temp);

            vis[xx][yy][timee] = ;

        }

    }

}