int main(void) {
int n1 [7]={1,2};
int n2 [5]={3,4,5,6,7};
int l1=2;
int l2=sizeof(n2)/sizeof(n2[0]);

cat_data(n1,n2,l2,l1);

for (int i=0;i<7;i++){
printf("data[%d]=%d\n",i,n1[i]);
}

return 0;
}
void cat_data(int *data1,const int*data2,int len2,int len1){
for (int i=0;i<len2;i++){
   data1[len1+i]=data2[i];
}
}