rt，悬一关，代码：

#include <bits/stdc++.h>

namespace Integer {
const std::string symbol = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
template <class T = int, int binary = 10> class BigInt {
private:
  T n;
  std::vector<T> a;
  bool f;

public:
  BigInt() { Init(); }
  T &operator[](int i) { return a[i]; }
  void Init() {
    n = f = 1;
    a.clear();
  }
  friend std::istream &operator>>(std::istream &is, BigInt &a) {
    std::string s;
    is >> s;
    a.n = s.size();
    if (s[0] == '-') {
      a.f = 0;
      a.n--, s.erase(0, 1);
    }
    for (int i = 0; i < a.n; i++) {
      a.a.push_back((s[a.n - i - 1] >= 'A' && s[a.n - i - 1] <= 'Z'
                         ? s[a.n - i - 1] - 'A' + 10
                         : s[a.n - i - 1] - '0'));
    }
    return is;
  }
  friend std::ostream &operator<<(std::ostream &os, BigInt a) {
    for (; a.n > 1 && !a[a.n - 1]; a.n--) {
    }
    if (!a.f) {
      os << '-';
    }
    for (int i = a.n - 1; i >= 0; i--) {
      os << symbol[a[i]];
    }
    return os;
  }
  bool operator<(BigInt x) {
    if (n == x.n) {
      for (int i = n - 1; i >= 0; i--) {
        if (a[i] != x[i]) {
          return a[i] < x[i];
        }
      }
    }
    return n < x.n;
  }
  BigInt operator-(BigInt x) {
    BigInt y, z = *this;
    if (z < x) {
      y.f = 0, std::swap(z, x);
    }
    y.n = z.n;
    y.a.resize(y.n);
    for (int i = 0; i < y.n; i++) {
      if (i >= std::min(z.n, x.n)) {
        y[i] = z[i];
        continue;
      }
      y[i] = z[i] - x[i];
    }
    for (int i = 0; i < y.n - 1; i++) {
      if (y[i] < 0) {
        y[i + 1]--;
        y[i] += binary;
      }
    }
    for (; !y[y.n - 1] && y.n > 1; y.n--) {
    }
    return y;
  }
};
}; // namespace Integer

using namespace std;
using namespace Integer;

int main() {
#ifndef ONLINE_JUDGE
  freopen("P2142_3.in", "r", stdin);
  freopen("P2142.out", "w", stdout);
#endif
  BigInt<> a, b;
  cin >> a >> b;
  cout << a - b;
  return 0;
}

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