You and a friend play a game where you start with a pile of 100 stones.

You alternate turns, and each turn you can take 1, 4 or 7 stones.

The player that takes the last stone (leaving nothing in the pile) wins!

Which player can guarantee a win?

The one who goes first
The one who goes second
Neither player

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The first player can take 4 stones, leaving 96 in the pile, which divides evenly by 8.

After that if the other player takes $n$ stones, the first player takes $8-n$ stones, leaving the pile with a number that is again divisible by 8.

This continues until the pile contains 0 stones, at which point the $\boxed{\text{player that went first}}$ has won.