View Compilation Error

0_0_36349103_5772.cpp: In function 'int main()':
0_0_36349103_5772.cpp:13:17: error: 'nga' was not declared in this scope
     if(a[i][j]>=nga[i-1][j]&&i!=1) dp[i][j]=dp[i-1][j]+1;
                 ^