C++ :

#include <cstdio>
using namespace std;
const int N(103);
struct point
{
    int r,c;
};
point cow[N];
bool East[N]={false},North[N]={false},Removed[N]={false};
int r,c,n;
bool safe()
{
    for(int i=1;i<=n;i++)
        if(!Removed[i])
        {
            East[i]=false;
            North[i]=false;
            for(int j=1;j<=n;j++)
                if(j!=i&&(!Removed[j]))
                {
                    if(cow[j].c>cow[i].c&&cow[j].r==cow[i].r)
                        East[i]=true;
                    if(cow[j].r<cow[i].r&&cow[j].c==cow[i].c)
                        North[i]=true;
                }
            if(East[i]&&North[i])
                return false;
        }
    return true;
}
int main()
{
    scanf("%d%d%d",&r,&c,&n);
    for(int i=1;i<=n;i++)
        scanf("%d%d",&cow[i].r,&cow[i].c);
    if(safe())
    {
        printf("0\n");
        return 0;
    }
    else
        for(int i=1;i<=n;i++)
        {
            Removed[i]=true;
            if(safe())
            {
                printf("1\n%d\n",i);
                return 0;
            }
            else Removed[i]=false;
        }
    printf("-1\n");
    return 0;
}