关于构造函数段错误的求助

struct Binary_indexed_array {
    int t[2000010],n;
	
    Binary_indexed_array(const int& a = 0) {
        n = a;
        memset(t,0,sizeof(t));
    }
	
    inline void add(const int& u,const int& k) {
        if (u < 1) return;
        for (int i = u; i <= n; i += lowbit(i)) t[i] += k;
    }
	
    inline int query(const int& u) {
        int ans = 0;
        for (int i = u; i >= 1; i -= lowbit(i)) ans += t[i];
        return ans;
    }
}st,nd;

int main() {
    n = input();
    c = input();
    q = input();
    st = Binary_indexed_array(c);
    nd = Binary_indexed_array(c);
    
    ... //省略其它代码，因为确定是上面5行错了
    
    return 0;
}