I used the solution given in
Troubling converting string to long long in C
to convert a string to long long in C. I am using Microsoft Visual Studio 2012.
On compiling I am getting the error
LNK2019: unreslved external symbol _+atoll referenced in function _main.
#include <stdio.h>
#include <stdlib.h>
int main(void) {
char s[30] = { "115" };
long long t = atoll(s);
printf("Value is: %lld\n", t);
return 0;
}