Approach s.p.s dp[x][y] : $\sum \limits_x \sum \limits_y v(x_i, y_i)$ for $1 \le x_i \le x , 1 \le y_i \le y$ (It is defined to be 0 if x or y are less than 1) Therefore dp[x][y] = dp[x - 1][y] + dp[x][y - 1] - dp[x - 1][y - 1]. So, Summation (x1, y1) to (x2, y2) equal to dp[x2, y2] - dp[x2, y1 - 1] - dp[x1 - 1, y2] + dp[x1 - 1, y1 - 1] Code #include #define fastio ios_base::sync_with_stdio(0), ..