Adding four numbers is easy. Adding a hundred is not, and a conversation does not stop at four. The input goes up by the same step every turn, and a run of numbers like that has an equation: multiply the number of turns by the next number up, halve it, then scale by the step. Work the small case by hand first, then check the equation against what you got. Two numbers decide the total: k, what one turn adds, and n, how many turns there have been. k is fixed by the agent, so shortening its answers drops every total, while n is the conversation itself, and because it appears twice, doubling it does not double the total.
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