View Compilation Error

0_0_28201762_14252.cpp: In function 'int main()':
0_0_28201762_14252.cpp:15:16: error: 'strlen' was not declared in this scope
    k = strlen(a)
                ^
0_0_28201762_14252.cpp:34:4: error: 'else' without a previous 'if'
    else
    ^