```ts

const MODULUS = 1000000007;

/** The nth Fibonacci number, modulo 1000000007. */
export function fibMod(n: number): number {
  if (n < 2) {
    return n;
  }

  let a = 0, b = 1, sum;
  for (let i = 2; i <= n; ++i) {
    sum = (a + b) % MODULUS;
    a = b;
    b = sum;
  }

  return b;
}
```