WA on Subtask #1 求助

#include <cstdio>
#include <algorithm>
using namespace std;
int n, m, q, a[305][305], op, x1, x2, y1, y2, c;
int tree[305][305][105];

static constexpr int lowbit(int x) {
    return x & (-x);
}

void change(int x, int y, int c, int val) {
    for(int i = x; i <= n; i += lowbit(i)) {
		for(int j = y; j <= m; j += lowbit(j)) {
            tree[i][j][c] += val;
        }
    }
}

int search(int x, int y, int c) {
    int res = 0;
    for(int i = x; i > 0; i -= lowbit(i)) {
        for(int j = y; j > 0; j -= lowbit(j)) {
            res += tree[i][j][c];
        }
    }
    return res;
}

int main() {
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= n; j++) {
            scanf("%d", &a[i][j]);
            change(i, j, a[i][j], 1);
        }
    }
    scanf("%d", &q);
    while(q--) {
        scanf("%d", &op);
        if(op == 1) {
            scanf("%d%d%d", &x1, &y1, &c);
            change(x1, y1, a[x1][y1], -1);
            change(x1, y1, c, 1);
            a[x1][y1] = c;
        } else if(op == 2) {
			scanf("%d%d%d%d%d", &x1, &x2, &y1, &y2, &c); 
            printf("%d\n", search(x2, y2, c)
                   - search(x1 - 1, y2, c)
                   - search(x2, y1 - 1, c)
                   + search(x1 - 1, y1 - 1, c));
        }
    }
    return 0;
}