Inserarea primei linii, intre oricare doua linii consecutive ale unei matrice

#include <iostream>
using namespace std;

int main()
{
    int n, m, i, j, a[101][101];
    cin>>n>>m;
    for(i=1; i<=n*2-1; i++)
    {
        for(j=1; j<=m; j++)
        {
            cin>>a[i][j];
        }
        i++;
        for(j=1; j<=m; j++)
            a[i][j]=a[1][j];
    }
    for(i=1; i<=n*2-1; i++)
    {
        for(j=1; j<=m; j++)
            cout<<a[i][j]<<" ";
        cout<<endl;
    }
    return 0;
}