How many different years did Marty McFly travel to in all of the Back to the Future movies?
4
3
3
3
3
3
2
3
2
4
3
2
4
5
3
2
4
5
3
2
4
5
3
2
4
5
3
2
4
5
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
2
6
4
5
1
3
2
6
4
5
1
0
3
2
6
4
5
1
3
2
0
6
4
5
1
3
2
6
4
5
0
1
3
2
6
4
5
7
1
0
2
6
4
5
7
1
2
0
6
9
4
5
7
1
2
6
9
4
5
0
7
1
2
6
9
4
5
7
1
0
8
6
9
4
5
7
1
8
6
9
5
7
1
8
6
9
7
1
10
8
6
9
ten
7
1
10
8
6
9
7
ten
1
10
8
6
9
7
1
10
8
ten
6
9
11
7
1
10
8
6
9
ten
11
7
10
8
6
9
11
7
ten
10
8
13
6
9
11
7
14
10
8
13
ten
9
11
7
14
10
8
13
9
ten
11
7
14
10