实验一 C语言开发环境使用和数据类型，运算符，表达式

#include<stdio.h>
int main(){
    int n, r1, r2, r3, r4;
    
    n = 100;
    
    r1 = n*(n+1)/2;
    r2 = (n+1)*n/2;
    r3 = n/2*(n+1);
    r4 = (n+1)/2*n;
    
    printf("n = %d\n", n);
    printf("r1 = %d\n", r1);
    printf("r2 = %d\n", r2);
    printf("r3 = %d\n", r3);
    printf("r4 = %d\n", r4);
    
    return 0;
}