View Compilation Error

0_0_18389012_21861.cpp: In function 'int main()':
0_0_18389012_21861.cpp:39:19: error: 'strlen' was not declared in this scope
   int L=strlen(S+1);
                   ^
0_0_18389012_21861.cpp:65:23: error: 'memset' was not declared in this scope
   memset(S,0,sizeof(S));
                       ^