View Compilation Error

0_0_27021385_18733.cpp:2:1: error: 'vector' does not name a type
 vector<long long>f;
 ^
0_0_27021385_18733.cpp: In function 'void coprime(int)':
0_0_27021385_18733.cpp:12:12: error: 'f' was not declared in this scope
     memset(f,0,sizeof(f));
            ^
0_0_27021385_18733.cpp: In function 'int main()':
0_0_27021385_18733.cpp:42:18: error: 'f' was not declared in this scope
             sum+=f[i]*(n/i);
                  ^