foo.cpp: In function 'void RPRP()':
foo.cpp:11:18: error: 'srand' was not declared in this scope
  srand(time(NULL));
                  ^
foo.cpp:12:9: error: 'rand' was not declared in this scope
  t=rand()%MD+50;
         ^
foo.cpp: In function 'void getans(char*)':
foo.cpp:34:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while (i<strlen(ch)){
                    ^
foo.cpp: At global scope:
foo.cpp:88:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
foo.cpp: In function 'int main()':
foo.cpp:98:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (j=0;j<strlen(ex);j++)
                      ^
foo.cpp:114:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (j=0;j<strlen(in);j++)
                       ^