906+901+904+892+902+895=900×6+6+1+4-8+2-5=540+13-13=540
900+6+900+1+900+4+900-8+900+2+900-5=900×6＋(6+1+4-8+2-5)=5400+(6+1+4+2-8-5)=5400+(13-13)=5400
