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ADA University - January 13 - Segment Tree

Dima and array

Mother gave Dima as a present an array of length n. The array is not simple, but special. Dima can choose two numbers i and d (1in, -1000d1000), and the element with index i magically becomes equal to d. Dima plays with his array, and mother gives his questions time from time - what is the sum of all the numbers in array with indexes from f to t inclusive? Dima easily managed this problem, but what about you?


The first line contains two integers n and q (1n5 * 105, 1q105) - the number of elements in array and the total number of operations. In the next line n numbers are given: a1, a2, ..., an (-1000ai1000) - the initial state of array. The next q lines contain the operations and queries. The first character in the line can be either = or ?. If the line starts with =, this is an assignment operation. Next values are i and d, their restrictions are given earlier. If the line starts with ?, this is a query. Then go numbers f and t (1f, tn).


For each query print on a separate line the sum of the numbers in array with indexes from f to t inclusive.

Time limit 1 second
Memory limit 128 MiB
Input example #1
3 3
1 2 3
? 1 3
= 3 2
? 1 3
Output example #1
Author Egor Kulikov
Source Winter School Kharkov 2012