View Compilation Error

0_0_36164936_1029.cpp:11:1: error: 'unordered_map' does not name a type
 unordered_map<int, int> mp1, mp2, mp3;
 ^
0_0_36164936_1029.cpp: In function 'void init()':
0_0_36164936_1029.cpp:14:25: error: 'maxn' was not declared in this scope
     for (int i = 0; i < maxn; i++) {
                         ^
0_0_36164936_1029.cpp:15:9: error: 'mp1' was not declared in this scope
         mp1[(int)(i * C)] = (int)(i * C) + i;
         ^
0_0_36164936_1029.cpp:16:9: error: 'mp2' was not declared in this scope
         mp2[i] = (int)(i * C);
         ^
0_0_36164936_1029.cpp:17:9: error: 'mp3' was not declared in this scope
         mp3[(int)(i * C) + i] = (int)(i * C);
         ^