按题意直接模拟即可。

AC code：

#include <bits/stdc++.h>
using namespace std;

int main() {
    freopen("pairs.in", "r", stdin);
    freopen("pairs.out", "w", stdout);
    int n;
    cin >> n;
    int b = 0, c = 0;
    for (int i = 1; i <= n; i++)
    {
        string s;
        cin >> s;
        if (s == "XZ") {
            b++, c++;
        }
        if (s == "ZX") {
            b--, c++;
        }
    }
    int a = n + abs(b) / 2 + c / 2;
    cout << a << endl;
    return 0;
}