Comparing 2 Strings in C

Hi all.
I am trying to create a program which will compare 2 strings.Find the first character which is equal between them and save it on the third string.If it doesnt find any character it will save a -1.
My code always prints a -1... :(
Here is my code,I dont know what I am doing wrong.If anybody has any idea,plz help me.

Code:

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#include <stdio.h>
#define MAX 1000
void any(char s1[],char s2[],char s3[]);
int main()
{
    char string1[MAX],string2[MAX],string3[MAX];
    printf("Jepni stringen 1\n");
    scanf("%s",& string1);  //saving string 1
    printf("Jepni stringen 2\n");
    scanf("%s",& string2);  //saving string 2
    any(string1,string2,string3); /*comparing characters from string 2 to string 1 and saving the places where they are equal on third string*/
    printf("%d",string3[0]); //printing the first character of the third string
    return 0;
}
void any(char s1[],char s2[],char s3[])
{
    int i,j,k;
    k=0;
    for(j=0;j!='\0';j++)
    {
                        for(i=0;i!='\0';i++)
                        {
                                            if(s2[j]==s1[i])
                                            {
                                                            s3[k]=i;
                                                            j++;
                                                            k++;
                                                            }
                                                            }
                                                            }
                                                            s3[k]=-1;
                                                            }

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Found The answer should have put s2[j] and s1[i] are diferrent from \0.