Защита от дурака. Как правильно сделать?

[svatorus]

Суть в том, что если вместо цифр при вводе А1, А2, В1, В2 вводить буквы, то прога игнорит дальнейшую сортировку данных и выводит все подряд . Как организовать защиту от подобного ввода? Препод по любому прикопается.

Собственно место проблемы:
void time(void)
{
cout<<"please, enter hour of A\n";
cin>>a1;
cout<<"Please, enter minute of A\n";
cin>>a2;
cout<<"please, enter hour of B\n";
cin>>b1;
cout<<"Please, enter minute of B\n";
cin>>b2;
cout<<"\n";
cout<<"\n";
}


Вся прога:

#include "stdafx.h"
#include "iostream"
#include <conio.h>
#include <iomanip>
#include <stdio.h>
using namespace std;

int a1,b1,a2,b2,i,t1,t2,t3,p,f=0,f1;
char gorod[20];
struct qwerty
{
int yesno;
char vector[20];
int number;
int time_c;
int time_m;
int time;
};
void city(void);
void time(void);

int main()
{

qwerty rasp[20]={
{1,"Kiev",666,10,15,6},
{1,"Tobolsk",79,14,56,48},
{1,"Volgograd",14,17,15,3},
{0,"Tumen",174,12,36,79},
{1,"Kiev",312,21,24,46},
{0,"Cheboksary",147,22,47,75},
{0,"Krasnodar",135,10,45,6},
{1,"Tobolsk",798,1,15,89},
{1,"Tumen",789,7,45,47},
{0,"Cheboksary",47,15,48,79},
{0,"Tumen",96,19,14,69},
{0,"Cheboksary",5,13,15,52},
{1,"Tumen",144,16,2,4},
{1,"Kiev",999,2,58,47},
{1,"Volgograd",89,3,17,19},
{0,"Tobolsk",4,14,32,5},
{0,"Krasnodar",458,23,31,74},
{1,"Kiev",457,6,58,46},
{1,"Tumen",969,7,14,47},
{1,"Cheboksary",141,3,43,26}};

city();
time();
if (((a1)>23)||((b1)>23))
{
cout<<"Incorrectly time, please enter again\n";
cout<<"\n";
time();
}
if (((a2)>59)||((b2)>59))
{
cout<<"Incorrectly time, please enter again\n";
cout<<"\n";
time();
}

t2=a1*60+a2;
t3=b1*60+b2;
for (i=0;i<=19;i++)
{
f1=1;
t1=rasp[i].time_c*60+rasp[i].time_m;
if ((p>=t2)&(p<=t3))
{
if (strcmp(gorod, rasp[i].vector)==0)
{
f=f+1;
if (rasp[i].yesno==1)
{
cout<<"Availability\n";
cout<<"Yes\n";
cout<<"Direction of train\n";
cout<<rasp[i].vector;
cout<<"\n";
cout<<"train number\n";
cout<<rasp[i].number;
cout<<"\n";
cout<<"departure time\n";
cout<<rasp[i].time_c;
cout<<":";
cout<<rasp[i].time_m;
cout<<"\n";
cout<<"travel time\n";
cout<<rasp[i].time;
cout<<"\n";
cout<<"\n";
cout<<"\n";
}
else
{
cout<<"There are no seats on the train number";
cout<<" ";
cout<<rasp[i].number;
cout<<"\n";
cout<<"\n";
}
}
}
}
if (f==0)
cout<<"Unfortunately, at a specified time no trains heading in this direction\n";
cout<<"\n";
cout<<"\n";

return 0;
}
void city(void)
{

cout<<"Please select a destination city\n";
cout<<"1.Kiev 2.Tobolsk 3.Volgograd 4.Cheboksary 5.Tumen 6.Krasnodar\n";
cin>>gorod;
}
void time(void)
{
cout<<"please, enter hour of A\n";
cin>>a1;
cout<<"Please, enter minute of A\n";
cin>>a2;
cout<<"please, enter hour of B\n";
cin>>b1;
cout<<"Please, enter minute of B\n";
cin>>b2;
cout<<"\n";
cout<<"\n";
}

[FelixXXI]

Я бы сделал так:

	cout<<"please, enter hour of A\n";
	int A;
	while(!(cin>>A))
	{
		cin.clear();
		while(cin.get()!='\n')
			continue;
		cout<<"\aInput error. ";
	}

[svatorus]

Благодарю! Дико выручил.

[Blade]

Сообщение от svatorus

Защита от дурака. Как правильно сделать?

...

int main()
{
  ...

  std::cout << "Вы дурак?" << std::endl;

  std::string result;
  std::cin >> result;

  if (result != "нет")
  {
    return 1;
  }

  ...
}