Language: C++

#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) (x = max(x,y))
#define mins(x,y) (x = min(x,y))
#define limit(x,l,r) max(l,min(x,r))
#define lims(x,l,r) (x = max(l,min(x,r)))
#define isin(x,l,r) ((l) <= (x) && (x) < (r))
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcountll
#define uni(x) x.erase(unique(rng(x)),x.end())
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
#define show(x) cout<<#x<<" = "<<x<<endl;
#define PQ(T) priority_queue<T,v(T),greater<T> >
#define bn(x) ((1<<x)-1)
#define dup(x,y) (((x)+(y)-1)/(y))
#define newline puts("")
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
typedef long long int ll;
typedef unsigned uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
inline int in() { int x; scanf("%d",&x); return x;}
template<typename T>inline istream& operator>>(istream&i,v(T)&v)
{rep(j,sz(v))i>>v[j];return i;}
template<typename T>string join(const v(T)&v)
{stringstream s;rep(i,sz(v))s<<' '<<v[i];return s.str().substr(1);}
template<typename T>inline ostream& operator<<(ostream&o,const v(T)&v)
{if(sz(v))o<<join(v);return o;}
template<typename T1,typename T2>inline istream& operator>>(istream&i,pair<T1,T2>&v)
{return i>>v.fi>>v.se;}
template<typename T1,typename T2>inline ostream& operator<<(ostream&o,const pair<T1,T2>&v)
{return o<<v.fi<<","<<v.se;}
template<typename T>inline ll suma(const v(T)& a) { ll res(0); for (auto&& x : a) res += x; return res;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#define dame { puts("-1"); return 0;}
#define yn {puts("Yes");}else{puts("No");}
const int MX = 200005;
#define RET(ans) {cout<<ans<<endl;return 0;} 

    // 二次元ベクターの基本
    /*
    vector<vector<int>> dp; // 宣言
    dp.resize(n); // 1次元めの要素数決定
    dp[i].push_back(int); // プッシュバック
    rep(i,n){
        sort(dp[i].begin(),dp[i].end()); // 二次元めを昇順ソート
    }
    */

    // 整数スキャン（複数）
    /*
    int x,y,z;
    scanf("%d%d%d",&x,&y,&z);

    // n個の整数のスキャン
    /*
    ll a[n] = {};
    rep(i,n){
        scanf("%lld",&a[i]);
    }
    */

    // 文字列スキャン
    /*
    string s; cin >> s;
    */

    // n個の文字列スキャン
    /*
    vector<string> slist;
    rep(i,n){
        string s; cin >> s;
        slist.push_back(s);
    }
    */

int main() {
    int h,w;
    cin >> h,w;
    int count[26] = {};
    rep(i,h){
        string s;
        cin << s;
        int a = 'a';
        rep(j,w){
            count[(int)s[j]-a]++;
        }
    }
    
    int one = 0;
    int two = 0;
    int four = 0;
    if(h%2==1&&w%2==1){
        one = 1;
        two =(h-1)/2+(w-1)/2;
        h--;
        w--;
    }
    if(h%2==1){
        two = w/2;
        h--;
    }
    if(w%2==1){
        two = h/2;
        w--;
    }
    four = (h/2)*(w/2);

    rep(i,26){
        while(count[i]>0){
            if(count[i]>=4){
                if(four>0){
                    four--;
                    count[i] -= 4;
                }else{
                    two -= 2;
                    count -= 4;
                }
            }else if(count[i]>=2){
                two--;
                count[i] -= 2;
            }else{
                one--;
                count[i]--;
            }
        }
    }

    if(four==4&&two==0&&one==0)yn;
    return 0;
}
 
 


Compiler output:
a.cc: In function 'int main()':
a.cc:98:13: error: no match for 'operator<<' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'std::string' {aka 'std::__cxx11::basic_string<char>'})
   98 |         cin << s;
      |         ~~~ ^~ ~
      |         |      |
      |         |      std::string {aka std::__cxx11::basic_string<char>}
      |         std::istream {aka std::basic_istream<char>}
a.cc:40:37: note: candidate: 'template<class T> std::ostream& operator<<(std::ostream&, const std::vector<_Tp>&)'
   40 | template<typename T>inline ostream& operator<<(ostream&o,const v(T)&v)
      |                                     ^~~~~~~~
a.cc:40:37: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::vector<_Tp>'
   98 |         cin << s;
      |                ^
a.cc:44:50: note: candidate: 'template<class T1, class T2> std::ostream& operator<<(std::ostream&, const std::pair<_T1, _T2>&)'
   44 | template<typename T1,typename T2>inline ostream& operator<<(ostream&o,const pair<T1,T2>&v)
      |                                                  ^~~~~~~~
a.cc:44:50: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::pair<_T1, _T2>'
   98 |         cin << s;
      |                ^
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1715:5: note: candidate: 'template<class _Ch_type, class _Ch_traits, class _Bi_iter> std::basic_ostream<_CharT, _Traits>& std::__cxx11::operator<<(std::basic_ostream<_CharT, _Traits>&, const sub_match<_Bi_iter>&)'
 1715 |     operator<<(basic_ostream<_Ch_type, _Ch_traits>& __os,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1715:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:41:
/usr/include/c++/14/cstddef:125:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator<<(byte, _IntegerType)'
  125 |     operator<<(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:125:5: note:   template argument deduction/substitution failed:
a.cc:98:9: note:   cannot convert 'std::cin' (type 'std::istream' {aka 'std::basic_istream<char>'}) to type 'std::byte'
   98 |         cin << s;
      |         ^~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:763:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, basic_string_view<_CharT, _Traits>)'
  763 |     operator<<(basic_ostream<_CharT, _Traits>& __os,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:763:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/bits/basic_string.h:4077:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 4077 |     operator<<(basic_ostream<_CharT, _Traits>& __os,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:4077:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/bitset:1687:5: note: candidate: 'template<class _CharT, class _Traits, long unsigned int _Nb> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const bitset<_Nb>&)'
 1687 |     operator<<(std::basic_ostream<_CharT, _Traits>& __os,
      |     ^~~~~~~~
/usr/include/c++/14/bitset:1687:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
In file included from /usr/include/c++/14/bits/ios_base.h:46,
                 from /usr/include/c++/14/streambuf:43,
                 from /usr/include/c++/14/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/14/iterator:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:54:
/usr/include/c++/14/system_error:339:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const error_code&)'
  339 |     operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e)
      |     ^~~~~~~~
/usr/include/c++/14/system_error:339:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
In file included from /usr/include/c++/14/memory:80,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:56:
/usr/include/c++/14/bits/shared_ptr.h:70:5: note: candidate: 'template<class _Ch, class _Tr, class _Tp, __gnu_cxx::_Lock_policy _Lp> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const __shared_ptr<_Tp, _Lp>&)'
   70 |     operator<<(std::basic_ostream<_Ch, _Tr>& __os,
      |     ^~~~~~~~
/usr/include/c++/14/bits/shared_ptr.h:70:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:563:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _CharT)'
  563 |     operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:563:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/ostream:573:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, char)'
  573 |     operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:573:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/ostream:579:5: note: candidate: 'template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, char)'
  579 |     operator<<(basic_ostream<char, _Traits>& __out, char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:579:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<char, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/ostream:590:5: note: candidate: 'template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, signed char)'
  590 |     operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:590:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<char, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/ostream:595:5: note: candidate: 'template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, unsigned char)'
  595 |     operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:595:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<char, _Traits>'
   98 |         cin << s;
      |                ^
/usr/include/c++/14/ostream:654:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const _CharT*)'
  654 |     operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:654:5: note:   template argument deduction/substitution failed:
a.cc:98:16: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'std::basic_ostream<_CharT, _Traits>'
   98 |         cin << s;
      |                ^
In file included from /usr/include/c++/14/ostream:1022:
/usr/include/c++/14/bits/ostream.tcc:307:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_Char