View Compilation Error

0_0_35157102_19859.cpp: In function 'int main()':
0_0_35157102_19859.cpp:8:21: error: cannot convert 'std::string {aka std::basic_string<char>}' to 'const char*' for argument '1' to 'size_t strlen(const char*)'
   int n = strlen(str);
                     ^