Language: C++

// template version 1.12
using namespace std;
#include <iostream>
#include <bits/stdc++.h>

// varibable settings
#define infile "../test/sample-1.in"
#define int long long //{{{
const int INF=1e18;
const int MOD=1e9+7; //}}}

// define basic macro {{{
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _rrep(i,n) rrepi(i,0,n)
#define rrepi(i,a,b) for(int i=(int)((b)-1);i>=(int)(a);--i)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define each(i,a) for (auto&& i : a)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define uni(x) sort(all(x));x.erase(unique(all(x)),x.end())
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x)-A.begin())
#define posu(A, x) (upper_bound(all(A),x)-A.begin())
template<class T> inline void chmax(T &a, const T &b) { if((a) < (b)) (a) = (b); }
template<class T> inline void chmin(T &a, const T &b) { if((a) > (b)) (a) = (b); }

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int,int> pii;
typedef tuple<int,int,int> iii;

template<typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast { Fast(){ std::cin.tie(0); ios::sync_with_stdio(false); } } fast;

#if defined(PCM) || defined(LOCAL)
  #include "lib/dump.hpp"
#else
  #define dump(...) 42
  #define dump_1d(...) 42
  #define dump_2d(...) 42
#endif
//}}}

int L, A, B, M;
int mod;
struct mint {
  int x;
  mint(int x=0):x(x%mod){}
  mint& operator+=(const mint a) {
    (x += a.x) %= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    (x += mod-a.x) %= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res+=a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res-=a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res*=a;
  }
};
ostream& operator<<(ostream& os, const mint& a){
  os << a.x;
  return os;
}


mint pow_(mint b, int x){/*{{{*/
  if (x==1) return b;
  if (x%2==0){
    mint t = pow_(b, x/2);
    return t*t;
  }
  else{
    return pow_(b, x-1)*b;
  }
}/*}}}*/

mint f(int x, int d){
  if (x==1) return 1;
  if (x%2==0){
    mint p = f(x/2, d);
    return (p + (pow_(pow_(10,d), (x/2))*p));
  }
  else{
    mint p = f(x-1, d);
    return (p + pow_(pow_(10, d), (x-1)));
  }
}

mint g(int x, int d){
  if (x==1) return pow_(10,d);
  mint ans = 0;
  if (x%2==0){
    int y = x/2;
    mint p = g(y, d);
    ans += p;
    ans += p * pow_(pow_(10,d),y);
    ans += f(y, d) * y * pow_(pow_(10,d),(y+1));
    return ans;
  }
  else{
    ans += g(x-1, d) + x * pow_(pow_(10,d), x);
    return ans;
  }
}

pii num(int d){/*{{{*/
  int m=1;
  rep(i,d) m*=10;
  if ((m-1)-A<0) return mp(-1,-1);
  int n = ((m-1)-A)/B;

  int last = min(n, L-1);

  m /= 10;
  int prelast;
  if ((m-1)-A<0) {
    prelast = -1;
  }
  else{
    n = ((m-1)-A)/B;
    prelast = min(n, L-1);
  }
  return mp(prelast, last);
}/*}}}*/


int solve(){
  cin>>L>>A>>B>>M;
  mod = M;
  dump(mod);

  mint ans = 0;
  rep(d, 1, 19){
    int fst,last;
    tie(fst,last) = num(d);
    fst++;
    int n = last - fst + 1;
    if (n==0) continue;

    ans *= pow_(pow_(10,d), n);
    ans += f(n, d) * (mint(A)+(mint(last)*mint(B)));
    if (n>1) ans -= g(n-1, d) * mint(B);
  }
  cout << ans << endl;

  return 0;
}

signed main() { //{{{
#ifdef INPUT_FROM_FILE
  std::ifstream in(infile);
  std::cin.rdbuf(in.rdbuf());
#endif
  solve();
  return 0;
} //}}}


Compiler output:
a.cc: In function 'mint g(long long int, long long int)':
a.cc:123:26: error: no match for 'operator*' (operand types are 'long long int' and 'mint')
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                        ~ ^ ~~~~~~~~~~~~~~~~~~~
      |                        |       |
      |                        |       mint
      |                        long long int
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:4:
/usr/include/c++/14/complex:400:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const complex<_Tp>&)'
  400 |     operator*(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:400:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::complex<_Tp>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/complex:409:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const _Tp&)'
  409 |     operator*(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:409:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::complex<_Tp>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/complex:418:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const _Tp&, const complex<_Tp>&)'
  418 |     operator*(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:418:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   'mint' is not derived from 'const std::complex<_Tp>'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   'mint' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   'mint' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::valarray<_Tp>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   mismatched types 'const std::valarray<_Tp>' and 'long long int'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:123:46: note:   'mint' is not derived from 'const std::valarray<_Tp>'
  123 |     ans += g(x-1, d) + x * pow_(pow_(10,d), x);
      |                                              ^