#include <stdio.h>

int main()
{
    int x = 0,y = 0;
    unsigned int size = 0;
    char name[50] = {0};
    unsigned int len = 0;

    printf("Enter the size = ");
    scanf("%u",&size);

    fflush(stdin);
    //Ask name
    printf("Enter the size = ");
    fgets(name,size,stdin);

    len = strlen(name);

    for(x=(size/2); x<=size; x+=2)
    {
        for(y=1; y<(size-x); y+=2)
        {
            printf(" ");
        }

        for(y=1; y<=x; ++y)
        {
            printf("*");
        }

        for(y=1; y<=(size-x); ++y)
        {
            printf(" ");
        }

        for(y=1; y<=x; ++y)
        {
            printf("*");
        }

        printf("\n");
    }

    for(x=size; x>=1; --x)
    {
        for(y=x; y<size; ++y)
        {
            printf(" ");
        }
        if(x == size)
        {
            for(y=1; y<=((size * 2)-len)/2; ++y)
            {
                printf("*");
            }

            fputs(name,stdout);
            for(y=((size * 2)-len)/2; y< size; ++y)
            {
                printf("*");
            }
        }
        else
        {
            for(y=1; y<=(x*2)-1; ++y)
            {
                printf("*");
            }
        }

        printf("\n");
    }

    return 0;
}

Output: