```ts
const MODULUS = 1000000007;

/** The nth Fibonacci number, modulo 1000000007. */
export function fibMod(n: number): number {
  if (n < 0) {
    throw new Error('Input must be a non-negative integer');
  }
  let a = 0;
  let b = 1;
  let result = 0;

  for (let i = 2; i <= n; i++) {
    const temp = (a + b) % MODULUS;
    result = i === 2 ? 1 : result;
    [a, b] = [b, temp];
  }
  return result;
}
```