0_0_39183430_3579.cpp: In function 'int main()': 0_0_39183430_3579.cpp:20:43: error: 'M' was not declared in this scope 20 | printf("%d\n",sum[x2*m+y2]-sum[x2*M+y1-1]-sum[m*(x1-1)+y2]+sum[m*(x1-1)+y1-1]); | ^