#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int n, m;
    cin >> n >> m;

    vector<pair<int, int>> instructions;
    for (int i = 0; i < m; ++i) {
        char comma;
        int a, b;
        cin >> a >> comma >> b;
        instructions.push_back({a, b});
    }

    sort(instructions.begin(), instructions.end());

    int additional_instructions = 0;
    vector<int> min_values(n + 1, INT_MAX);

    for (auto& inst : instructions) {
        min_values[inst.second] = min(min_values[inst.second], min_values[inst.first]);
    }

    for (auto& inst : instructions) {
        if (min_values[inst.first] >= min_values[inst.second]) {
            additional_instructions++;
            min_values[inst.second] = min(min_values[inst.second], min_values[inst.first]);
        }
    }

    cout << additional_instructions << endl;

    return 0;
}

求助各位大佬，为何编译出错？