C++ Program for getting LCM

#include<iostream>
using namespace std;

int main()
{
const int N=20; //value of N may be increased here
int numbers[N],LCM;
bool flag=1;
for( int i=0 ; i<N ; i++ )
{
do
{
cout << "Enter number "
<< (i+1)
<< ": ";
cin >> numbers[i]; }while(numbers[i]<0);
}
for( int i=0 ; i<N ; i++ )
{
if( numbers[i]==0 )
{
flag=0;
}
}
if(!flag)
{
cout << "\nL.C.M is zero(0)."
<< endl;
}
else
{
int large,prod;
large=numbers[0];
prod=1;
for( int i=0 ; i<N ; i++ )
{
if( numbers[i]>large )
large=numbers[i];
prod*=numbers[i];
}
int index;
for( int i=large ; i<=prod ; i++ )
{
/*if( i%numbers[0]==0 && i%numbers[1]==0 && i%numbers[2]==0 )
{
LCM=i;
break;
} */
index=-1;
for( int j=0 ; j<N ; j++ )
{
if( i%numbers[j]!=0 )
{
index=j;
break;
}
}
if( index==-1 )
{
LCM=i;
break;
}
}
cout << "\nL.C.M is: "
<< LCM
<< ".\n";
}

return 0;
}