本地能过，结果是0分。。显示第一个位置上是ascii-56，求助~

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int main()
{
    char a[100],ans[100];
    char last;
    int b,c,n;
    cin>>n;
    getchar();
    while(n--)
    {
        fgets(a,sizeof(a),stdin);
        if(a[0]=='a'||a[0]=='b'||a[0]=='c')
                { last=a[0];
                   a[0]=' ';
                }
    sscanf(a,"%d %d",&b,&c);
    switch(last)
    {
        case 'a' : sprintf(ans,"%d+%d=%d",b,c,b+c);break;
        case 'b' : sprintf(ans,"%d-%d=%d",b,c,b-c);break;
        case 'c' : sprintf(ans,"%d*%d=%d",b,c,b*c);break;
    }
      printf("%s\n%d",ans,strlen(ans));
    if(n!=0)
        printf("\n");

    }
    return 0;
}