const getGets = (arr) => {
    let index = 0;

    return () => {
        const toReturn = arr[index];
        index += 1;
        return toReturn;
    };
};
// this is the test
const test = [
    6, -26, -25, -28, 31, 2, 27
];


const gets = this.gets || getGets(test);
const print = this.print || console.log;

// code


const n = +gets();
const arr = new Array();

for(let i = 0; i < n; i++) {
    arr.push(gets());
}

var result = -1;

for (var index = 0; index < arr.length - 1; index++) {
    if((index == 0) || (index == arr.length - 1)){
        continue;
    }else{
        if ((arr[index - 1] < arr[index]) && (arr[index] > arr[index + 1])){
            result = index;
            break;
        }
    }
}
print(result);