The teacher asked five students to recite 1000 common English words. It is known that A students have 950 backs, B students have 925 backs, C students have 900 backs, D students have 875 backs, and E students have 850 backs. So how many words are at least among the 1000 English words that the five students all recited correctly.
老师要求五位学生背诵常见的1000个英文单词．已知A生背对950个，B生背对925个，C生背对900个，D生背对875个，E生背对850个．那么在这1000个英文单词中至少有多少个单词五位学生全背对了．
<gadget id="calculator">1_000 * 5</gadget>
<output>5_000</output>

<gadget id="calculator">950 + 925 + 900 + 875 + 850</gadget>
<output>4_500</output>

<gadget id="calculator">5_000 - 4_500</gadget>
<output>500</output>

<result>500</result>