View Compilation Error

0_0_10273509_16847.cpp: In function `int main()':
0_0_10273509_16847.cpp:9: error: `strlen' undeclared (first use this function)
0_0_10273509_16847.cpp:9: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10273509_16847.cpp:12: error: `i' undeclared (first use this function)
0_0_10273509_16847.cpp:16: error: `n' undeclared (first use this function)