```ts
const MODULUS = 1000000007;

export function fibMod(n: number): number {
  if (n < 2) {
    return n;
  }
  let prev1 = 0, prev2 = 1, current;
  for(let i = 2; i <= n; i++) {
    current = (prev1 + prev2) % MODULUS;
    prev1 = prev2;
    prev2 = current;
  }
  return current;
}
```