#include<bits/stdc++.h>

using namespace std;

const int N = 1e4 + 10;

typedef long long ll;

char a[N];

string ans[N<<1];

string tmp1 ,tmp2;

bool dp[N][2];

int cur ,num = 1;

int main()

{

    scanf("%s",a);

    int len = strlen(a);

    if(len <= 6)

    {

        printf("0\n");

        return 0;

    }

    dp[len-1][0] = 1;

    tmp1 = "";

    tmp1 += a[len-2];

    tmp1 += a[len-1];

    ans[cur++] = tmp1;

    if(len > 7)

    {

        dp[len-1][1] = 1;

        tmp1 = "";

        tmp1 += a[len-3];

        tmp1 += a[len-2];

        tmp1 += a[len-1];

        ans[cur++] = tmp1;

    }

    for(int i = len - 3 ;i >= 6 ;i--)

    {

        tmp1 = "";

        tmp1 += a[i-1];

        tmp1 += a[i];

        tmp2 = "";

        tmp2 += a[i+1];

        tmp2 += a[i+2];

        dp[i][0] = dp[i+3][1] || dp[i+2][0] && (tmp1 != tmp2);

        if(dp[i][0])

            ans[cur++] = tmp1;

        if(i == 6)

            continue;

        tmp1 = "";

        tmp1 += a[i-2];

        tmp1 += a[i-1];

        tmp1 += a[i];

        tmp2 = "";

        tmp2 += a[i+1];

        tmp2 += a[i+2];

        tmp2 += a[i+3];

        dp[i][1] = dp[i+2][0] || dp[i+3][1] && (tmp1 != tmp2);

        if(dp[i][1])

            ans[cur++] = tmp1;

    }

    sort(ans ,ans + cur);//排序

    for(int i = 1 ; i < cur ; i++)

    {

        if(ans[i] != ans[i-1])//并去重

            num++;

    }

    printf("%d\n",num);

    cout<<ans[0]<<"\n";

    for(int i = 1 ; i < cur ; i++)

    {

        if(ans[i] != ans[i-1])

            cout<<ans[i]<<"\n";

    }

    return 0;

}