编写一个程序，计算 1 + 2 + 3 + 4 + … + N的累加和，并把累加和以十进制形式显示出来。（不能使用公式计算“累加和=N×（N+1）/2”，必须使用程序实现循环累加来计算）。-Write a program to calculate the 1++++ 4 ... the+ N accumulation, and the sum of the decimal form is displayed. (Can not use the formula " sum = N (N+1)/2, you must use the program cycle accumulate to calculate).