```ts
const MODULUS = 1000000007;

export function fibMod(n: number): number {
  if (n < 2) {
    return n;
  }

  let a = 0;
  let b = 1;
  for (let i = 2; i <= n; i++) {
    const temp = (a + b) % MODULUS;
    a = b;
    b = temp;
  }
  return b;
}
```