View Compilation Error

0_0_20214843_4847.cpp: In function 'int main()':
0_0_20214843_4847.cpp:17:32: error: 'strlen' was not declared in this scope
             int key=strlen(temp)-1;
                                ^
0_0_20214843_4847.cpp:40:32: error: 'strlen' was not declared in this scope
             int key=strlen(temp)-1;
                                ^