int i,j;
int cnt = 0, N;
cout << "请输入正整数N：";
cin >> N;
for (i = 1; (j=i) < N; i++)
    while (j != 0)
        if (j % 10 == 3){
            cnt +=1;
            __________;
        }
        else
            __________;
cout << cnt << " ";