Language: C++

#include <iostream>
#include <vector>
#include <string>
#include <cstdlib>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <stack>
#include <math.h>
#include <map>
#define Z class
#define ln cout<<'\n'
#define ll long long
#define rep(i, n) for(int i = 0; i < (n); ++i)
//ASCII a=97, A=65
// int H[N]; rep(i,N) scanf("%d", &H[i]);
// int max_x = *std::max_element(x.begin(), x.end());
// int min_y = *std::min_element(y.begin(), y.end());
using namespace std;
template<class T> inline bool chmax(T& a, T b){ if(a < b) { a=b; return 1; }return 0;}
template<class T> inline bool chmin(T& a, T b){ if(a > b) { a=b; return 1; }return 0;}
template<Z A>void pr(A a){cout<<a;ln;}
template<Z A,Z B>void pr(A a,B b){cout<<a<<' ';pr(b);}
template<Z A,Z B,Z C>void pr(A a,B b,C c){cout<<a<<' ';pr(b,c);}
template<Z A,Z B,Z C,Z D>void pr(A a,B b,C c,D d){cout<<a<<' ';pr(b,c,d);}
template<Z A>void PR(A a,ll n){rep(i,n){if(i)cout<<' ';cout<<a[i];}ln;}

int GCD(int a, int b) { return b ? GCD(b, a%b) : a; }
const long long INF = 1LL << 60;

int main(){
    string a,b; cin >> a >> b;
    cout << (a-1)*(b-1) << endl;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:33:15: error: no match for 'operator-' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
   33 |     cout << (a-1)*(b-1) << endl;
      |              ~^~
      |              | |
      |              | int
      |              std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/string:48,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:33:16: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   33 |     cout << (a-1)*(b-1) << endl;
      |                ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:33:16: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   33 |     cout << (a-1)*(b-1) << endl;
      |                ^
a.cc:33:21: error: no match for 'operator-' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
   33 |     cout << (a-1)*(b-1) << endl;
      |                    ~^~
      |                    | |
      |                    | int
      |                    std::string {aka std::__cxx11::basic_string<char>}
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:33:22: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   33 |     cout << (a-1)*(b-1) << endl;
      |                      ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:33:22: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   33 |     cout << (a-1)*(b-1) << endl;
      |                      ^