View Compilation Error

0_0_24004086_6697.cpp: In function 'void get_next()':
0_0_24004086_6697.cpp:9:18: error: 'strlen' was not declared in this scope
  int m = strlen(a);
                  ^
0_0_24004086_6697.cpp: In function 'void kmp(int)':
0_0_24004086_6697.cpp:17:18: error: 'strlen' was not declared in this scope
  int n = strlen(b);
                  ^
0_0_24004086_6697.cpp: In function 'int main()':
0_0_24004086_6697.cpp:31:24: error: 'scanf' was not declared in this scope
     while(scanf("%s", a)){
                        ^
0_0_24004086_6697.cpp:35:18: error: 'printf' was not declared in this scope
  printf("%d", ans);
                  ^