View Compilation Error

0_0_35640497_17907.cpp: In function 'int main()':
0_0_35640497_17907.cpp:8:2: error: expected ';' before 'string'
  string s1,s2;
  ^
0_0_35640497_17907.cpp:9:13: error: 's1' was not declared in this scope
  while(cin>>s1>>s2)
             ^
0_0_35640497_17907.cpp:9:17: error: 's2' was not declared in this scope
  while(cin>>s1>>s2)
                 ^
0_0_35640497_17907.cpp:15:14: error: 'l2' was not declared in this scope
    for(int j=l2-1;j>=0;j--)
              ^
0_0_35640497_17907.cpp:24:11: error: 'l2' was not declared in this scope
   cout<<f[l2-1]<<endl;
           ^