a=randperm(20)
b=a(1:n)
c=1:20
sum(c(b))

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#include"stdio.h"
main()
{
    int i,sum=0,a[20];
    printf("请输入二十个数：");
    for(i=0;i<20;i++)
    {
      scanf("%d",&a[i]);
      sum+=a[i];
    }
    printf("%d",sum);
}