C sscanf turn begin of string each time

I've to scan characters in string in order but in that example

char s[8]={"ab"};
char a,b;

sscanf(s,"%c", &a);
sscanf(s,"%c", &b);

printf("%c%c", a, b);

it prints aa. but i need to it prints ab. How can i fix it? Should I print string to file and read from file?