View Compilation Error

0_0_18077195_19998.cpp: In function 'int main()':
0_0_18077195_19998.cpp:51:93: error: 'k' was not declared in this scope
                         dp[i][i+len]=(dp[i][i+len]+(dp[i][j-1]*dp[j+1][i+len])%mod*c[j - i][k - i]) % mod)%mod;
                                                                                             ^