#include <iostream>#include <vector>using namespace std;bool verify(vector<int> iv, int inx){ int size = iv.size(); int sum, sub; sum = inx + iv[inx]; sub = inx - iv[inx]; for(int i = 1; i < size; i++) { if(i + iv[i] == sum || i - iv[i] == sub) if(i != inx) return false; } return true;}int main(){ int n; cin>>n; vector<int> ivec(n+1); int x, y; int counter = n; while(counter--) { cin>>x>>y; ivec[x] = y; } int temp; counter = 0; int i, j, k; for(i = 1; i < n+1; i++) for(j = i+1; j < n+1; j++) for(k = j+1; k < n+1; k++) { temp = ivec[i]; ivec[i] = ivec[j]; ivec[j] = ivec[k]; ivec[k] = temp; if(verify(ivec, i) && verify(ivec, j) && verify(ivec, k)) counter++; temp = ivec[i]; ivec[i] = ivec[j]; ivec[j] = ivec[k]; ivec[k] = temp; if(verify(ivec, i) && verify(ivec, j) && verify(ivec, k)) counter++; temp = ivec[i]; ivec[i] = ivec[j]; ivec[j] = ivec[k]; ivec[k] = temp; } cout<<counter<<endl;}
