Answer:
#include <stdio.h>
#include <string.h>
int main(void) {
 char simonPattern[50];
 char userPattern[50];
 int userScore;
 int i;
 userScore = 0;
 scanf("%s", simonPattern);
 scanf("%s", userPattern);
 for(i = 0;simonPattern[i]!='\0';i++){
     if(simonPattern[i]!=userPattern[i]){
      userScore=i;
      break;
   }
 }
 printf("userScore: %d\n", userScore);
 return 0;
}
Explanation: