[JavaScript] inclusion-exclusion principle
\n\nvar stringCount = function(n) {\n    const mod = 1_000_000_007n; \n    \n    const pow = function(x, p, m) {\n        let ans = 1n; \n        for (; p; p >>
\n```\nvar stringCount = function(n) {\n    const mod = 1_000_000_007n; \n    \n    const pow = function(x, p, m) {\n        let ans = 1n; \n        for (; p; p >>= 1) {\n            if (p & 1) ans = ans * x % m; \n            x = x * x % m; \n        }\n        return ans; \n    }\n    \n    const bn = BigInt(n); \n    return ((pow(26n, n, mod) - (75n+bn)*pow(25n, n-1, mod) + (72n+2n*bn)*pow(24n, n-1, mod) - (23n+bn)*pow(23n, n-1, mod)) % mod + mod) % mod; \n};\n```
['JavaScript']