知道错哪里了但是不知道怎么调

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#include <map>
#include <vector>
#define mr make_pair
#define ff first
#define ss second

using namespace std;
using ll = long long;
const int N = 2e5 + 5;

int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
int n, m, nx, ny, ans;
bool lt[102][102], vis[102][102];
vector<pair<int, int>> data[102][102];
pair<int, int> ft;
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> m;
    lt[1][1] = 1;
    for (int i = 1; i <= m; i++) {
        int a, b, c, d;
        cin >> a >> b >> c >> d;
        data[a][b].push_back(mr(c, d));
    }

    queue<pair<int, int>> q;
    pair<int, int> last;
    q.push(mr(1, 1));
    while (!q.empty()) {
        ft = q.front();
        vis[ft.first][ft.second] = 1;
        q.pop();
        for (auto i : data[ft.first][ft.second]) {
            if (!lt[i.first][i.second]) {
                lt[i.first][i.second] = 1;
                // ans++;
                // cout << i.first << " " << i.second << "\n";last = i;
            }
            last = i;
        }
        for (int i = 0 ; i < 4; i++) {
            nx = ft.first + dx[i];
            ny = ft.second + dy[i];

            if (nx < 1 || ny < 1 || nx > n || ny > n || !lt[nx][ny] || vis[nx][ny]) {
                continue;
            }

            q.push(mr(nx, ny));
        }
    }

    for (auto i : data[last.first][last.second]) {
            if (!lt[i.first][i.second]) {
                lt[i.first][i.second] = 1;
                // ans++;
            }
        }

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            // cout << lt[i][j];
            if (lt[i][j]) ans++;
        }
        // cout << "\n";
    }

    cout << ans;

    return 0;
}