{"raw_statement":[{"iden":"problem statement","content":"There is a staircase with $N$ steps. Takahashi is now standing at the foot of the stairs, that is, on the $0$\\-th step. He can climb up one or two steps at a time.\nHowever, the treads of the $a_1$\\-th, $a_2$\\-th, $a_3$\\-th, $\\ldots$, $a_M$\\-th steps are broken, so it is dangerous to set foot on those steps.\nHow many are there to climb up to the top step, that is, the $N$\\-th step, without setting foot on the broken steps? Find the count modulo $1\\ 000\\ 000\\ 007$."},{"iden":"constraints","content":"*   $1 \\leq N \\leq 10^5$\n*   $0 \\leq M \\leq N-1$\n*   $1 \\leq a_1 < a_2 < $ $...$ $< a_M \\leq N-1$"},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$ $M$\n$a_1$\n$a_2$\n $ .$\n $ .$\n $ .$\n$a_M$"},{"iden":"sample input 1","content":"6 1\n3"},{"iden":"sample output 1","content":"4\n\nThere are four ways to climb up the stairs, as follows:\n\n*   $0 \\to 1 \\to 2 \\to 4 \\to 5 \\to 6$\n*   $0 \\to 1 \\to 2 \\to 4 \\to 6$\n*   $0 \\to 2 \\to 4 \\to 5 \\to 6$\n*   $0 \\to 2 \\to 4 \\to 6$"},{"iden":"sample input 2","content":"10 2\n4\n5"},{"iden":"sample output 2","content":"0\n\nThere may be no way to climb up the stairs without setting foot on the broken steps."},{"iden":"sample input 3","content":"100 5\n1\n23\n45\n67\n89"},{"iden":"sample output 3","content":"608200469\n\nBe sure to print the count modulo $1\\ 000\\ 000\\ 007$."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}