Цкил не үшін алғы шартты деп аталды

1)
#include <iostream>

using namespace std;

int main() {
  cout << "Сколько Вам лет?" << endl;
  int age;
  string s;
  cin >> age >> s;
}
2)
#include <iostream>

using namespace std;

int main() {
  cout << "Сколько Вам лет?" << endl;
  int age;
  cin >> age;
  if(age < 0) cout << "wrong" << endl;
  else if(age >= 18) cout << "yes" << endl;
  else cout << "no" << endl;
}

3)
#include <iostream>

using namespace std;

int main() {
 int a;
 cin >> a
 if(a%2 == 0) cout << "четное" << endl;
 else cout << "нечетное" << endl;
}

4)
#include <iostream>

using namespace std;

int main() {
 int a,b,c;
 string s = "";
 cin >> a >> b >> c;
 if(a == b && a == c) cout << "равносторонний" << endl;
 else {
    if (a==b || a == c || b == c) s += "равнобедренный";
    if( a*a == (b*b+c*c) || b*b == (a*a+c*c) || c*c == (a*a+b*b))
           s+= "прямоугольный";
    if(s == '') cout << "обычный" << endl;
    else cout << s << endl;
  }
}
 
 

#include <iostream>

#include <math.h>

using namespace std;

int main()

{

double a, b, c, x1, x2, d;

 

do{

 cout << "Input a: ";

 cin >> a;

 if (a == 0) {

  cout << "Error! a = 0! This isn't a square equation! Try again" << endl;

 }

} while (a == 0);

cout << "Input b: ";

cin >> b;

cout << "Input c: ";

cin >> c;

 

d = b * b - 4. * a * c;

 

if (d < 0) {

 cout << "No roots";

 return 1;

}  

else if (d == 0) {

 cout << "x = " << -b / 2. / a;

 return 2;

}

else {

 cout << "x1 = " << (-b + sqrt(d)) / 2. / a << ", x2 = " << (-b - sqrt(d)) / 2. / a;

 return 0;

}

}