Delete unordered_map registry when looping

#include <unordered_map>
#include <iostream>

int total = 1;

typedef std::unordered_map<char, bool> mapa;
typedef std::unordered_map<int, mapa> stu_mapa;
stu_mapa STU_mapa;

void add(char letter, bool verdade) {
    std::unordered_map<char, bool> ma_pa;
    ma_pa[letter] = verdade;
    STU_mapa.insert(stu_mapa::value_type(total, ma_pa));
    total ++;
    return;
}

int main() {
    std::cout << "Inicio" << std::endl;
    add('a',false);
    add('b',false);
    add('c',false);
    add('d',true);
    add('e',true);
    add('f',false);

    for(stu_mapa::reverse_iterator j = STU_mapa.rbegin(); j!=STU_mapa.rend(); j++) {
        std::unordered_map<char, bool> ma_pa = j->second;
        std::unordered_map<char, bool>::const_iterator k = ma_pa.begin();
        if(k->second == true) {
            std::cout << "delete " << j->first << std::endl;
            STU_mapa.erase(j->first);
            j--;
        }
        else {
            std::cout << j->first << std::endl;
        }
    }

    std::cout << "desce" << std::endl << std::endl;

    for(stu_mapa::reverse_iterator j = STU_mapa.rbegin(); j!=STU_mapa.rend(); j++) {
        std::cout << j->first << std::endl;
    }

    system("pause");
    return 1;
}