View Compilation Error

0_0_37135135_23393.cpp: In function 'int main()':
0_0_37135135_23393.cpp:24:29: error: 'M' was not declared in this scope
         for (int k = 1; k < M; ++k) for (int i = 0; i < n; ++i) for (int j = 0; j < n; ++j) dp[k | (1 << i) | (1 << j)][i] = min(dp[k | (1 << i) | (1 << j)][i], dp[j][i] + dp[k | (1 << j)][j]);
                             ^