{"raw_statement":[{"iden":"problem statement","content":"You are given a trapezoid. The lengths of its upper base, lower base, and height are $a$, $b$, and $h$, respectively.\n\n![image](https://atcoder.jp/img/arc061/1158e37155d46a42e90f31566478e6da.png)An example of a trapezoid\n\nFind the area of this trapezoid."},{"iden":"constraints","content":"*   $1≦a≦100$\n*   $1≦b≦100$\n*   $1≦h≦100$\n*   All input values are integers.\n*   $h$ is even."},{"iden":"input","content":"The input is given from Standard Input in the following format:\n\n$a$\n$b$\n$h$"},{"iden":"sample input 1","content":"3\n4\n2"},{"iden":"sample output 1","content":"7\n\nWhen the lengths of the upper base, lower base, and height are $3$, $4$, and $2$, respectively, the area of the trapezoid is $(3+4)×2/2 = 7$."},{"iden":"sample input 2","content":"4\n4\n4"},{"iden":"sample output 2","content":"16\n\nIn this case, a parallelogram is given, which is also a trapezoid."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}