#include <stdio.h>
int suma(char a[]) {
int i = 0;
while (a[i] != '\0' && a[i] != '\n') {
i++;
}
return i;
}
int sum(char a[], char b[]) {
char sizea = suma(a), sizeb = suma(b);
if (sizea > sizeb) {
return sizeb;
}
if (sizea < sizeb) {
return sizea;
}
if (sizea == sizeb) {
int size = sizea;
for (int i = 0; i < size; i++) {
if (a[i] != b[i]) {
return i;
}
}
}
return -1;
}
int main() {
char a[1001] , b[1001], answer = 0;
int m,n;
int i=0,t=0;
while((m=getchar())!=' '){
a[i]=m;
i++;
}
while((n=getchar())!=EOF){
b[t]=n;
t++;
}
//fgets(a,1001, stdin);
//fgets(b,1001, stdin);
// printf("a = %s\nb = %s\n",a,b);
answer = sum(a, b);
printf("%d", answer);
return 0;
}