```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 === '' ||
      typeof price !== 'number' ||
      price <= 0 || !Number.isInteger(price)
    ) {
      throw Error('Invalid die specification');
    }
    if (table.has(fragment)) {
      throw Error(`Duplicate fragment: ${fragment}`);
    }
    table.set(fragment, price);
  }
  return table;
}

export function stampCover(label: string, dies: [string, number][]): number {
  if (typeof label !== 'string' || label === '') {
    throw Error('Invalid label');
  }

  const table = stampTable(dies);

  const dp = new Array(label.length + 1).fill(Infinity);
  dp[0] = 0;

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

  return dp[label.length] === Infinity ? -1 : dp[label.length];
}
```