Count Vowels Permutation LeetCode solution in Rust

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impl Solution {
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  pub fn count_vowel_permutation(n: i32) -> i32 {
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    const MOD: i64 = 1e9 as i64 + 7;
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    let mut a = 1;
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    let mut e = 1;
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    let mut i = 1;
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    let mut o = 1;
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    let mut u = 1;
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    for _ in 1..n {
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      let a_next = e;
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      let e_next = (a + i) % MOD;
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      let i_next = (a + e + o + u) % MOD;
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      let o_next = (i + u) % MOD;
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      let u_next = a;
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      a = a_next;
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      e = e_next;
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      i = i_next;
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      o = o_next;
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      u = u_next;
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    }
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    ((a + e + i + o + u) % MOD) as i32
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  }
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}