what pauls is saying is
val1*10+val2=val3
int val1=1;
int val2=2;
int val3 = operation that will give this variable the value 1 followed by 2 (12) and not the sum.
build and array of char(string) long as the first+seconds strings+1, copy the strings (with string's class method or a loop) and finally add the final character '\0' (this means "end of string" for all the functions in the String.h, and also for printf, scanf, ecc...)