View Compilation Error

0_0_27165974_17486.cpp: In function 'int main()':
0_0_27165974_17486.cpp:114:35: error: 'strlen' was not declared in this scope
     string key(input, strlen(input) - 1);
                                   ^
0_0_27165974_17486.cpp:121:35: error: 'strlen' was not declared in this scope
     string key(input, strlen(input) - 1);
                                   ^