{"raw_statement":[{"iden":"problem statement","content":"We have $N+1$ integers: $10^{100}$, $10^{100}+1$, ..., $10^{100}+N$.\nWe will choose $K$ or more of these integers. Find the number of possible values of the sum of the chosen numbers, modulo $(10^9+7)$."},{"iden":"constraints","content":"*   $1 \\leq N \\leq 2\\times 10^5$\n*   $1 \\leq K \\leq N+1$\n*   All values in input are integers."},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$ $K$"},{"iden":"sample input 1","content":"3 2"},{"iden":"sample output 1","content":"10\n\nThe sum can take $10$ values, as follows:\n\n*   $(10^{100})+(10^{100}+1)=2\\times 10^{100}+1$\n*   $(10^{100})+(10^{100}+2)=2\\times 10^{100}+2$\n*   $(10^{100})+(10^{100}+3)=(10^{100}+1)+(10^{100}+2)=2\\times 10^{100}+3$\n*   $(10^{100}+1)+(10^{100}+3)=2\\times 10^{100}+4$\n*   $(10^{100}+2)+(10^{100}+3)=2\\times 10^{100}+5$\n*   $(10^{100})+(10^{100}+1)+(10^{100}+2)=3\\times 10^{100}+3$\n*   $(10^{100})+(10^{100}+1)+(10^{100}+3)=3\\times 10^{100}+4$\n*   $(10^{100})+(10^{100}+2)+(10^{100}+3)=3\\times 10^{100}+5$\n*   $(10^{100}+1)+(10^{100}+2)+(10^{100}+3)=3\\times 10^{100}+6$\n*   $(10^{100})+(10^{100}+1)+(10^{100}+2)+(10^{100}+3)=4\\times 10^{100}+6$"},{"iden":"sample input 2","content":"200000 200001"},{"iden":"sample output 2","content":"1\n\nWe must choose all of the integers, so the sum can take just $1$ value."},{"iden":"sample input 3","content":"141421 35623"},{"iden":"sample output 3","content":"220280457"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}