500000500000
告诉你一个方法,头加尾法,把1加上1000000,得1000001,2加上999999,得1000001,依次类推,总共有500000个1000001,所以得到500000500000
利用等差数列求和公式可得:(1+1000000)*1000000/2=500000500000
1+2+3+4+5+6+7+8+9+10+11+12一直加到1000000
=500000*1000001
=500000500000
=(1+1000000)/2*1000000
=500000500000
=500000×1000001=500000500000