Finding the length of the last word input in C. At the while loop part, the if statement never reaches the else part, how to fix that?

Finding the length of the last word input in C. At the while loop part, the if statement never reaches the else part, how to fix that? The output for the input "Hello world" should be 5

#include<stdio.h>
#include<string.h>

int lsl(char s[]){
    int L;
    char str[5000]={0};
    gets(str);
    
    L = strlen(str);
    int i = L-1;
    while(i>=0){
        if(str[i]!=" ") i--;
        else break;
    }
    printf("%s:\n",str);
    printf("%d:\n",L);
    printf("%d:\n",i);
    printf("%d:\n",L-1-i);
    return L-1-i;
} 

void main(){
    char s[5000];
    lsl(s);
}