题目的意思是已知等差数列和 图片说明 为 图片标题 ，项数n为m，公差d为2，求首项a1

#include<stdio.h>
#include<string.h>

int main(int argc, char const *argv[])
{
    int m = 0;
    char strb[999]={0};
    
    while (scanf("%d", &m) != EOF)
    {
        memset(strb, 0x00, sizeof(strb));
        int sum = m*m*m;
        int a1= sum/m - (m - 1);
        sprintf(strb, "%d", a1);
        for (int i = 1; i < m; i++)
        {
            a1 += 2;
            strcat(strb, "+");
            sprintf(strb+strlen(strb), "%d", a1);
        }
        printf("%s\n", strb);
    }
    return 0;
}