C++ :

/* 枚举 4 个兵种与数字 1~4 的 24 种对应关系，取最大胜场 */
#include <cstdio>
#include <algorithm>
using namespace std;
int cnt[4][4];
int main(){
    int n;
    if(scanf("%d", &n) != 1) return 0;
    for(int i = 0; i < n; i++){
        int x, y;
        scanf("%d %d", &x, &y);
        if(x >= 1 && x <= 4 && y >= 1 && y <= 4) cnt[x - 1][y - 1]++;
    }
    int p[4] = {0, 1, 2, 3}, best = -1;
    do {
        int w = 0;
        for(int d = 0; d < 4; d++)
            for(int e = 0; e < 4; e++)
                if(p[e] == (p[d] + 1) % 4) w += cnt[d][e];
        if(w > best) best = w;
    } while(next_permutation(p, p + 4));
    printf("%d\n", best);
    return 0;
}