C Program to find first repeating character in a string

#include<stdio.h>
#include<string.h>
char FirstRepeatedChar(char *str){
int i;
int len=strlen(str)-1;
int count[256];
for(i=0;i<256;i++)
count[i]=0;

for(i=0;i<len;i++)
{
if(count[str[i]]==1){

printf("%c",str[i]);
break;
}
else count[str[i]]++;
}
if(i==len)
printf("\nNo characters found");
return 0;
}

int main()
{
char str[100];
int len;
char c;
printf("ENter string:");
fgets(str,100,stdin);
len=strlen(str)-1;
c=FirstRepeatedChar(str);


return 0;

}