#include <iostream>
#include <string>
#include <cstdlib>
 
int main()
{
  std::string str;
  int i;
 
  while (true) {
    std::cout << "数を入力してください" << std::endl;
    std::getline(std::cin, str);
//    i = std::stoi(str); // これは変な文字列の場合例外を投げるので使わない
    i = std::atoi(str.c_str()); // これだと例えば "1234abcd" みたいな入力では 1234 を返すがそこは勘弁してくださひ
    if (i != 0 || (i == 0 && str == "0")) // iが0でないか、0の場合はstrも"0"の場合抜ける
      break;
  }
  std::cout << i << "ですね？" << std::endl;
}
 

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

MTIzNGFiY2Q=

1234abcd