Rust comb pow
rust\nimpl Solution {\n    pub fn string_count(n: i32) -> i32 {\n        let n = n as i64;\n        const MOD: i64 = 1_000_000_007;\n        let qpow = |mut a: 
```rust\nimpl Solution {\n    pub fn string_count(n: i32) -> i32 {\n        let n = n as i64;\n        const MOD: i64 = 1_000_000_007;\n        let qpow = |mut a: i64, mut n: i64| -> i64 {\n            let mut ans: i64 = 1;\n            while n > 0 {\n                if n & 1 == 1 {\n                    ans = (ans * a % MOD) % MOD;\n                }\n                a = (a * a % MOD) % MOD;\n                n >>= 1;\n            }\n            ans\n        };\n        let mut res = qpow(26, n);\n        res = (res - ((n + 75) * qpow(25, n - 1) % MOD) + MOD) % MOD;\n        res = (res + ((2 * n + 72) * qpow(24, n - 1)) % MOD) % MOD;\n        ((res - ((n + 23) * qpow(23, n - 1)) % MOD + MOD) % MOD) as _\n    }\n}\n```
['Rust']