Language: C++

#include <iostream>
using namespace std;

// modint: mod 計算を int を扱うように扱える構造体
template<int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};


const int MOD = 1000000007;
using mint = Fp<MOD>;

int main() {
  
  mint n, k;
  cin >> n >> k;
  long long ans;
  for (int i = k; i < n+k; i++) {
  	ans += n*k -k*k + k + 1;
  }
    cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:68:7: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'mint' {aka 'Fp<1000000007>'})
   68 |   cin >> n >> k;
      |   ~~~ ^~ ~
      |   |      |
      |   |      mint {aka Fp<1000000007>}
      |   std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:24: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'bool&'
  170 |       operator>>(bool& __n)
      |                  ~~~~~~^~~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]'
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:25: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'short int&'
  174 |       operator>>(short& __n);
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:34: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'short unsigned int&'
  177 |       operator>>(unsigned short& __n)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]'
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:23: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'int&'
  181 |       operator>>(int& __n);
      |                  ~~~~~^~~
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:32: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'unsigned int&'
  184 |       operator>>(unsigned int& __n)
      |                  ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:24: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'long int&'
  188 |       operator>>(long& __n)
      |                  ~~~~~~^~~
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:33: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'long unsigned int&'
  192 |       operator>>(unsigned long& __n)
      |                  ~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:29: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'long long int&'
  199 |       operator>>(long long& __n)
      |                  ~~~~~~~~~~~^~~
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:38: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'long long unsigned int&'
  203 |       operator>>(unsigned long long& __n)
      |                  ~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:25: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'float&'
  219 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:26: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'double&'
  223 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:31: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'long double&'
  227 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:25: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'void*&'
  328 |       operator>>(void*& __p)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]'
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:32: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'}
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |                  ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:133:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  133 |       operator>>(ios_base& (*__pf)(ios_base&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:133:30: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'std::ios_base& (*)(std::ios_base&)'
  133 |       operator>>(ios_base& (*__pf)(ios_base&))
      |                  ~~~~~~~~~~~~^~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:352:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; __streambuf_type = std::basic_streambuf<char>]'
  352 |       operator>>(__streambuf_type* __sb);
      |       ^~~~~~~~
/usr/include/c++/14/istream:352:36: note:   no known conversion for argument 1 from 'mint' {aka 'Fp<1000000007>'} to 'std::basic_istream<char>::__streambuf_type*' {aka 'std::basic_streambuf<char>*'}
  352 |       operator>>(__streambuf_type* __sb);
      |                  ~~~~~~~~~~~~~~~~~~^~~~
In file included from /usr/include/c++/14/string:55,
                 from /usr/inc