0_0_25318125_13386.cpp: In function 'mtix mul(mtix, mtix)': 0_0_25318125_13386.cpp:20:40: error: no match for 'operator[]' (operand types are 'mtix' and 'int') c.a[i][j]+=(a.a[i][k]*b.a[k][j])%mod,c[i][j]%=mod; ^