```ts
const MODULUS = 1000000007;

export function fibMod(n: number): number {
  if (n < 2) {
    return n;
  }
  let a = 0, b = 1, c;
  for (let i = 2; i <= n; ++i) {
    c = (a + b) % MODULUS;
    a = b;
    b = c;
  }
  return b;
}
```