#include<iostream.h>
#include<conio.h>
#include<math.h>
int snt(int n)
{
      for (int i=2;i<=sqrt(double(n));i++)
      if (n%i==0)
      return 0;
      return 1;
}
main()
{
        int n;
        cout<<" nhap n= "; cin>>n;
        if (snt(n)) cout<<"la so ng to";
        else cout<<"khong la so ngto";
        getch();
}

#include<iostream.h>
#include<conio.h>

main()
{
        cout<<"                    Chuong trinh tinh tong va tick cua 2 ma tran\n\n\n\n";
        int m,n,p,q;
        cout<<"nhap so hang cua ma tran a: "; cin>>m;
        cout<<"nhap so cot cua ma tran a: "; cin>>n;
        int a[m][n],c[m][n];
        cout<<"nhap cac phan tu cua ma tran\n";
        cout<<endl;//cach dong nhin cho de
        for (int i=1;i<=m;i++)
            for (int j=1;j<=n;j++)
                {
                  cout<<"a["<<i<<"]["<<j<<"]= ";
                  cin>>a[i][j];
                }
        cout<<endl;
        cout<<"Nhap so hang cua ma tran b: "; cin>>p;
        cout<<"Nhap so cot cua ma tran b: "; cin>>q;
        int b[p][q],d[m][q];
        cout<<"nhap cac phan tu cua ma tran:\n";
        cout<<endl;//cach dong nhin cho de
        for (int i=1;i<=p;i++)
            for (int j=1;j<=q;j++)
                {
                     cout<<"b["<<i<<"]["<<j<<"]= ";
                     cin>>b[i][j];
                }
        cout<<endl;
        if ((m==p) && (n==q))
        {
           cout<<"Tong 2 ma tran a va b la: ";
           //tinh va in ra ma tran tong
           for (int i=1;i<=m;i++)
               {
                    cout<<endl;
                    for (int j=1;j<=n;j++)
                        {
                         c[i][j]=a[i][j] + b[i][j];
                         cout<<c[i][j]<<" ";
                        }
               }
        }
        cout<<endl<<endl;//xuong 2 dong
        if (n==p)
        {
                 cout<<"tick cua 2 ma tran la \n";
                 //tinh cac phan tu cua ma tran tick
                 for (int i=1;i<=m;i++)
                      {
                          for (int j=1;j<=q;j++)
                          {
                     d[i][j]=0;
                     for(int k=1;k<=p;k++)
                     d[i][j]=d[i][j]+a[i][k]*b[k][j];
                          }
                      }
                 //in ma tran tick       
                 for (int i=1;i<=m;i++)
                 {
                     cout<<endl<<endl;//xuong 2 dong
                     for (int j=1;j<=q;j++)
                    cout<<d[i][j]<<"   ";
                 }
                 cout<<endl;
        }
        else cout<<"2 ma tran nay khong the lam ry voi nhau dc. Chuc ban may man lan sau ;))";
        getch();
}