Multimap. Ошибка operator+ not implemented in type multimap

m[c[i]]++;

//---------------------------------------------------------------------------
#include <iostream.h>
#include <conio.h>
#include <map>
#include <algorithm>
#define N 200
//---------------------------------------------------------------------------
 
#pragma argsused
 
int i, a, j;
char c[N];
multimap<char, int> m;
int main()
{
for (int i=0; i<N;i++)
{
c[i]=0;
}
cout<<"Enter crypto"<<endl;
cin.getline(c,N);
for(int i=0;i<N;i++)
{
m[c[i]]++;
}
cout<<"\nRepeat rate: "<<endl;
multimap<char, int>::iterator t;
for(t=m.begin();t!=m.end();t++)
{
if((*t).first==0)continue;
{
cout<<(*t).first<<"-"<<(*t).second<<endl;
}
}
getch();
}
 
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
#include <iostream>
#include <map>
//---------------------------------------------------------------------------
 
using namespace std;
 
int main()
{
    
    const size_t N = 200;
 
    char c[N] = {};
 
    map<char, int> m;
 
    
    cout<<"Enter crypto"<<endl;
    cin.getline(c, N);
 
    for(const auto& i: c)
        ++m[i];
        
    cout<<"\nRepeat rate: "<<endl;
    for(const auto& pair: m)
        cout<<pair.first<<"-"<<pair.second<<endl;
}
//---------------------------------------------------------------------------