In a certain family, the father gives out pocket money to his children in the following way. Every month he chooses a number between 1 and 100, and then shares that amount of money equally between the seven children, giving them whole-number sums of money, and giving anything left over to charity. For instance, if he chose the number 30, he would give $4 to each child ($4 x 7 = $28) and $2 to charity. If the father realises after 100 months that every number between 1 and 100 (inclusive) has been used once, how much has he given to charity?