#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
/*
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if(a > 9 || b > 9)
        cout << -1;
    else
        cout << a * b;

    return 0;
}
*/

Measured memory_bytes: 256