i did not understand which test case is wrong help please!!!.

#include <stdio.h>

int main(void)

{ int a[100],n,t,i,sum,b,c=0,j;

scanf("%d",&t);

while(t–)

{ scanf("%d",&n);

for(i=0;i<n;i++)

scanf("%d",&a[i]);

for(i=0;i<n;i++)

{ for(j=i+1;j<n;j++)

{ b=a[i]*a[j];

sum=0;

while(b)

{ sum=sum+b%10;

b=b/10;

}

if(c<sum)

c=sum;

}

}

printf("%d\n",c);

}

return 0;

}