#include <bits/stdc++.h>   using namespace std;   int n, r[1010], c[1010], rc[1010], rr[1010], tr[1010], tc[1010], rtc[1010],       rtr[1010];   class portal {    public:     int ix, iy, ox, oy;   };   vector<portal> ans;   int main() {     scanf( %d , &n);     for (int i = 1; i <= n; i++) {       scanf( %d , &r[i]);       rr[r[i]] = i;     }     for (int i = 1; i <= n; i++) {       scanf( %d , &c[i]);       rc[c[i]] = i;     }     for (int i = 1; i <= n; i++) tr[i] = tc[i] = rtr[i] = rtc[i] = i;     for (int i = 1; i <= n; i++) {       if (tc[i] == rc[i] && tr[i] == rr[i]) continue;       ans.push_back((portal){i, rtc[rc[i]], rtr[rr[i]], i});       int t1 = tc[i], t2 = tr[i];       swap(tc[i], tc[rtc[rc[i]]]);       swap(tr[i], tr[rtr[rr[i]]]);       swap(rtc[rc[i]], rtc[t1]);       swap(rtr[rr[i]], rtr[t2]);     }     printf( %d n , ans.size());     for (portal x : ans) printf( %d %d %d %d n , x.ix, x.iy, x.ox, x.oy);     return 0;   }   