为什么这个会RE??

#include <stdio.h>
int main(){
    int i,K,j,sum = 0,t = 1,a[100001] = {0},b[100001] = {0};
    scanf("%d",&K);
    for (i = 1; i <= K; i++) a[i] = i;
    for (i = 1; i <= K; i++){
        for (j = 0; j <= t - 1; j++) if(i + j <= K) b[i + j] = a[t];    
        i+=j - 1; t++;
    }
    //for (i = 1; i <= K + 1; i++) printf("%d ",a[i]); printf("\n"); 
    //for (i = 1; i <= K + 1; i++) printf("%d ",b[i]); printf("\n"); 
    for (i = 1; i <= K; i++) sum+=b[i];
    printf("%d",sum);
    return 0;
}