```ts
export function stampTable(dies: [string, number][]): Map<string, number> {
  const table = new Map<string, number>();

  for (const [fragment, price] of dies) {
    if (typeof fragment !== 'string' || fragment.length === 0) {
      throw new Error('Fragment must be a non-empty string');
    }
    if (!Number.isInteger(price) || price <= 0) {
      throw new Error('Price must be a positive integer');
    }
    if (table.has(fragment)) {
      throw new Error(`Duplicate fragment: ${fragment}`);
    }
    table.set(fragment, price);
  }

  return table;
}

export function stampCover(label: string, dies: [string, number][]): number {
  if (typeof label !== 'string' || label.length === 0) {
    throw new Error('Label must be a non-empty string');
  }

  const table = stampTable(dies);
  const n = label.length;
  const dp = Array(n + 1).fill(Infinity);
  dp[0] = 0;

  for (let i = 1; i <= n; i++) {
    for (const [fragment, price] of table) {
      if (i >= fragment.length && label.slice(i - fragment.length, i) === fragment) {
        dp[i] = Math.min(dp[i], dp[i - fragment.length] + price);
      }
    }
  }

  return dp[n] === Infinity ? Infinity : dp[n];
}
```